How Phentermine Affects Your Period

Periods are a pain, literally, but we kind of like them being regular so we can anticipate when to schedule in the necessary couch-days and Netflix marathons. However, when you’re taking phentermine, your period can become irregular and your monthly symptoms may worsen due to the way phentermine affects your hormones. Here we explain how phentermine affects your period, and how to cope with these changes.

How Phentermine Affects Your Period

Although it is not listed as a side effect of phentermine, anecdotal evidence shows that many women experience changes to their period when taking the medication. Discussions on the phentermine forum indicate that the following changes have all been experienced by our forum users:

  • Missed periods (no menstrual flow for over 40 days)
  • Late periods (5 or more days overdue, according to usual cycle)
  • Early periods (5 or more days early, according to usual cycle)
  • Heavier or prolonged periods
  • Lighter or shorter periods
  • Spotting or intermittent bleeding between periods
  • Infrequent menstruation (only 4 to 9 periods in a year, medically known as Oligomenorrhea)
  • Frequent menstruation (more than 17 periods in a year, medically known as Polymenorrhea)
  • More severe symptoms – cramps, premenstrual syndrome (PMS), nausea, dizziness,

Essentially, these changes to your period all indicate irregular menstruation, whereby your monthly cycle and the symptoms which occur alongside it are different to the menstruation cycle that you used to experience before taking phentermine.  While these changes can be very concerning, we hope that knowing that many other women have experienced the same symptoms when taking phentermine helps to put your mind at ease – which is why the phentermine forum is such an important source of information and support for many phentermine users.

Why Does Phentermine Affect Your Period?

In much the same way that phentermine has been indirectly linked to hair loss, it is thought that the changes to your period occur alongside phentermine due to the way that weight loss can affect your hormones, which in turn affects your monthly cycle. Dramatic weight loss, which phentermine users often experience, causes a drop in the amount of estrogen in the body, as the release of estrogen is partially based on the amount of fat cells in the body. This decline in estrogen production can then cause changes to your menstrual cycle, resulting in irregular periods and can even cause your periods to stop completely.

An alternative theory is that the way in which phentermine stimulates your sympathetic nervous system to trigger the ‘fight or flight’ response can result in a reduction in the release of reproductive hormones, which would explain why some women taking phentermine may experience fewer periods than usual. However, irregular periods, heavier menstrual bleeding and spotting can also be explained by the way that phentermine in known to increase your heart rate. A faster heart-rate means increased blood flow and more build up in the ‘spiral arteries’ which support the endometrium of your uterus, which then degenerates to cause the onset of your period.

Another reason for an abnormal menstrual cycle is poor nutrition as a result of not eating a varied enough diet, possibly due to a lack of appetite while taking phentermine. Regardless of your weight or the amount of exercise you do, a lack of iron, zinc, and healthy fats in your diet can all cause changes to your period and an increase in the severity of menstrual symptoms such as cramps, dizziness and nausea.


How To Reduce These Symptoms

If you think that poor nutrition is contributing to your menstrual irregularity then taking a comprehensive multivitamin such as Phen Vites alongside your phentermine prescription will ensure that you’re getting all the nutrients you need for a healthy body, and this will also help to ease the symptoms of irregular periods, menstrual cramps, and other symptoms. In fact, making sure to get all the vitamins and minerals you need to keep healthy will also boost weight loss, as your body needs a variety of nutrients to burn calories and keep your metabolism going. As well as taking a multivitamin, you should try to eat a varied diet, being sure to include healthy foods rich in iron such as leafy greens, lean red meat and pumpkin seeds to help reduce some of these menstrual symptoms.

If you are sexually active and able to become pregnant then you should be using some kind of birth control as phentermine cannot be taken by women who are pregnant or trying to become pregnant. If your choice of contraceptive is an oral birth control pill then taking the pill continuously is one way to limit severe periods and other symptoms that come with menstruation, such as PMS and cramps. This method is often recommended by medical professionals to women with heavy or painful periods, but they do advise that you should have at least four periods a year to maintain the correct balance for future fertility. So, instead of taking the placebo pills or skipping your pill for a week, just move onto your next packet, but just be sure to give yourself a break from your birth control pill every couple of months. Avoiding having a period every month means that you will be able to get some relief from the effects that losing weight with phentermine can have on your menstrual cycle. Not to mention, skipping several periods can also help you to avoid the other symptoms of that time of the month, such as weight gain, bloating and cravings, so staying on track while taking phentermine is much easier too.

Lastly, if your period is often irregular and you have had difficulty losing weight in the past, as well as other symptoms such as fatigue, cramps, constipation, fertility problems or acne, then you may be suffering from an undiagnosed health issue, such as thyroid problems or Polycystic Ovary Syndrome (PCOS), which both affect the body’s hormone levels. Although losing weight with phentermine can help to relieve some of the symptoms of these conditions, it is advisable to be tested for these conditions, if only to rule them out as possibilities.


Although coping with irregular periods and more severe symptoms can be difficult, getting healthier by eating a more varied diet and losing weight with phentermine will help to resolve these issues in the long term. The good news is that when you get closer to your target weight your body should adjust to the new amount of hormones, and your periods should become more regular and the symptoms less severe.

Have your periods changed since you starting taking phentermine? Let us know by commenting below.


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107 Responses

  1. The first month I was taking it (May) I noticed my period was longer than normal. This month I was supposed to get it 6/14 but have yet to get it. I took a pregnancy test on the 17th that was negative and I have all the symptoms of my period coming as well has using protection in the form of condoms without any complications.

  2. Yes, my period has been severely impacted by phentermine. I initially lost 25 lbs in about 5 weeks with it. I have been bleeding heavily ever since – for over four weeks now with intermittent heavy large clotting for days at a time. I’ve had my cycle for 29 years (got it early at 10) and I’ve never had anything like this. I have had heavy periods before and I have several fibroids but they are not large yet never experienced anything like this – especially with the large clots for days. I’ve had to increase my iron intake because I’m getting weak and exhausted. I keeping reading it’s “a normal” side effect but when will it end?

    • Hi Amanda,
      What you describes sounds more serious than most people experience on phentermine – have you spoken to your doctor about this? The clotting sounds concerning, as does your significant loss of blood.

      • Hi im taking duromine and its my 4th capsule today. Can i use qlaira alongside with duromine?

        • Hi Ana!

          Yes, you can! There have not been any contraindications reported between the two. However, we do suggest you consult with your prescribing doctor when taking any medicine or supplement alongside phentermine, just in case!



      • Hi, OMG thanks godness that I found this article! I have beentaking phentermine for about 3 years. I take it regulary bc once I stop then I gain weight again so I start taking it over and over again. Like 2 years ago I started to have problems with my periods, heavy bleeding andspecially terrible cramps. Before that my period was always regular with nearly any pain and it lasted not more than 3 days. I started then to visit a gyn, etc and after some months of studies they decided to make me a laparascopy surgery to see what is going on and then I was diagnosticated with Endometriosis! I am on my 30\’s and never before I had any symptms of Endo, etc. Everything started after I started to take the phentermine pills regulary!!! . There is any study, or investigation aboutthis, nothing associate the uses of phen to the Endo but in my case I have been suspected that this pills has too much to do with it because in the months that I am taking the pills, my period get worst and the endo syms too! And everything started just after several months of being taking phentermine. Now reading this usuful article I am convinced that it was the phentermine what caused my Endo or at least what bring it out or made it to came out! I will stop taking it rightnow!! Thanks

    • I started taking phentermine a few weeks ago. My periods have been regular once a month but it’s changed since I started taking phentermine for weight loss. I thought I was going through the change of life until I started putting every thing together that I do. I am not on birth control pills, I do eat a regular healthy diet now, I also take a multivitamin daily, not to stress out as usual. Then I thought about it this morning – could this weight loss drug have anything to do with having irregular periods cause I only bleed when I take phentermine. So I went online and google up could phentermine cause irregular menstrual periods?”. Oh my GOD I was shocked to find out it does and to know other women experience this too was even more shocking. About 10 years ago I was taking phentermine from this weight loss clinic here in Milwaukee. They had prescribed phentermine to me and it worked well but I never missed a period or had two periods in a month like this when I was taking it 10 years ago. So now things change and so have the weight loss clinic prices. So I go into this name brand store and find it in there for a cheaper price and purchase it, it’s called fastin, same phentermine. Now I find out to help reduce this side effect I have to take the phen vites as well.

      • Hi Sally,
        That’s for your feedback about how your periods have changed as a result of taking phentermine. However, just so that you are aware, Fastin is not phentermine. There is some confusion over the name Fastin because when phentermine first went on sale in the 1970s it sold under the name Fastin, but the Fastin that is sold in stores today is a supplement and has nothing to do with the phentermine that is prescribed by doctors. This FAQ from our website explains the difference between Fastin and phentermine:

  3. Yep it sure did. I am 52 and haven’t had a period in over a year but after I started taking phentermine for a couple of days my period is so heavy its scary. I’m going to stop taking the Phentermine today but on a positive note it stopped my hot flashes and night sweats!!!!

  4. I’ve been on Phentermine for nearly 3 months now and I have not gotten my period. I took a pregnancy test and was negative. I do have all the symptoms of a period but nothing. But the medication is working so far.

    • Hi Sabrina,
      I wouldn’t be too worried, it seems that these kinds of changes are quite typical among women taking phentermine. Just be sure to eat a nutritious balanced diet and your period should return when your body gets used to the drug.


    • Hi Kayla,
      Late periods are quite common for many women taking phentermine so this is not a reason to be worried. If you are sexually active and could become pregnant then it is advisable to use contraceptives of some kind while taking phentermine. If you think you could be pregnant then you should do a pregnancy test and stop taking phentermine immediately if you are pregnant. With the bloating, this may be related to your late period and water retention, so be sure to drink lots of water and to avoid foods which can cause bloating such as salt, fizzy drinks, cruciferous veggies, dairy and chewing gum.

    • My cycle is 6 days late and I’m having all the symptoms of it coming such as bloating, headaches, and cramps. I haven’t taken a pregnancy test because the last time I had sex I was not ovulating. I started taking phentermine on July 7. So what I’m reading about your period being delayed can really be happening. Please help somebody!!

  6. I started phen on June 21 of this year as well as my period started that day. Period started heavy and ended in 6 days. After my trial phen of ten days I went a week without it. Between 6/30-7/6 I was sexually active and unprotected. I have an allergy to whatever is on the condoms and a latex allergy. I also cannot take birth control because it causes irregular heavy bedridden bleeding. I have been tested for everything ultrasounds the whole nine and I’m just fine down there. I went from 7/5 to 7/11 without taking the phen. I experienced some spotting on 7/6. On 7/12 I started back on the phen. I experienced spotting again on 7/19 a clear discharge on 7/20 and then in the afternoon heavy bleeding occurred. I had to leave work early and I have not been back to work. I have been experiencing cramping in my abdomen lower back glutes and thighs and legs. I’ve experienced nausea and vomitting as well. Even fatigue which I do not see how is possible because usually I’m awake while using phen. I am praying that it will lighten up by 7/25 so that I can go back to work. It is very heavy very red and lots of clotting. I experienced this in the past with birth control. A typical period without birth control and of course phen is 6-8 days medium to light flow with no abdominal cramping no nausea no dizziness no vomiting.

  7. I started Phenteime on June 26, my cycle was heavy. I’ve now been on it for approximately a month and a half, and now have had spotting. No nausea or other symptoms, and I’m super happy with my weight loss!!

    • Hi, I have the same problem, did you find any remedy to your problem with your prolonged period? I still have mine going and need it to stop. Have you tried any supplements?

  8. I was taking birth control pills before starting phentermine. This was to regulate my periods because they were too heavy. But now that I started phentermine they are not working my periods are heavy again. What can I do? I gained weight with the pills and got dark spots on my face. That’s why I decided to take phentermine. I have lost 38 pounds in five months. But now the problem is with my periods, I have anemia.

    • Hi Veronica,
      We think that it would be best to talk to your doctor or OBGYN about the problems with your period and how to manage them whilst taking phentermine.

    • I have a similar story. Stop the Darn Phentermine. That is exactly what’s messing your periods up. It manipulates your hormones. I am going to consult a Bariatric surgeon for Gastric Sleeve

  9. Started taking Phen one week from today and my period was supposed to come that Friday and it never did. Second week today, I have cramps like my period is coming but it has not. I feel a little nauseous and dizzy. I also feel bloated and I don’t think I have lost weight. I did take it once before like months ago and I did lose weight.

  10. My husband and I have been trying to conceive for over a year. I have had tests taken to check my thyroid and for pcos and they all came back healthy. However, my periods are so irregular, I never know when or if I am ovulating. My Dr. Suggested I lose weight, so now I am trying phentermine. I have been on it for 5 days now and have lost about a lb. a day and have been eating and drinking healthily. This morning, my period (which has been spotty for months) decided it would show up. I bled everywhere, it woke me from my sleep. It seems as if my blood has thinned? There were large clots. I am hoping that my body is trying to flush out the lining that has been building up due to lack of flow with my period. Here is hoping for regular future periods and healthy weight loss so that we may soon try for a baby. If this bleeding persists, should I discontinue phen?

    • Hi Kristina,
      As the article explains, irregular periods are common on phentermine, both in the sense that the user will often experience changes to what they used to expect from their period, but also that the period can come more or less often than might be considered in the normal range, and be particularly light or heavy. I would say that the explanation you’ve given as to why you think this period is heavy and with clotting sounds quite likely as you have previously experienced infrequent periods and spotting, so there may have been some build-up from previous months. I would discuss this with your doctor as he or she will be able to offer you advice about what to do if your period becomes more of a concern, as it may not be necessary to stop taking phentermine. Lastly, to ensure that your blood loss doesn’t affect your health and weight loss due to low iron levels, it could be a good idea to take iron supplements or make a point of eating iron-rich foods, as we explain here:
      I hope that helps!

    • As long as you are on Phentermine the bleeding will not stop. I am speaking from personal experience

  11. I have taken phentermine for 2 months and have had a large amount of hair loss, so I have quit taking it. I just read about the hair loss. I am now taking biotin tosee if I can get my hair to grow back

  12. I have been on the phentermine for 2 months. I have always had irregular periods so that is nothing new for me but I have had ovarian cramps for 3 weeks and excessive ovulation and discharge for the 3 weeks too. Side effect??

    • Hi Melanie,
      This is something we haven’t heard of before as a side effect so it could be a good idea to see your doctor about this, even if just to be reassured that it’s nothing to worry about.

  13. My period hasn\’t stopped after a week of taking phentermine. I’ve had my period for about 6 weeks now. Should I take iron and zinc supplements to help? I decided to stop taking phentermine 2 weeks after I noticed I still had my period. How do I regulate my hormones? What vitamins should I take? If someone knows please help. I don’t have access to any doctor or hospital at the moment, but I have access to a store where they sell vitamins. Thanks in advance!!!!

    • Did you figure anything out?

  14. I have the nexplanon implant in my arm for birth control and it has caused me to not have a period for nearly a year. Then on my second month on phen it starts and I’m super emotional and ill (one of the main reasons i wanted the implant) I just wish I could handle my emotions.

  15. I have PCOS. I took duromine to help me start to lose some weight because I really would like to get pregnant again.
    1) I have regular periods… like clock work… but I get terrible cramps and hectic bleeds and can barely walk for 2 days of my 7 day period. I throw up and get headaches… I do see a doc yearly…
    2)I have been like this since I was a child when my periods started.

    I stopped taking duromine daily… slowly weaned myself off it and found I have kept the 14kg I lost off with out any hard work.
    But … when i have my periods and I am in agony… I find taking a duromine takes the cramps away… it is almost a miraculous, within the hour effect… I go from sitting and rocking myself in pain to being normal.
    It doesn’t seem to thin my blood… it seems to ease the headaches… I am pretty much using duromine lately only for those 2 days of hell.
    Painkillers don’t have this effect on me…it just dulls the pain, and anything with aspirin in it will make my nose bleed at this time. I will discuss this with my doctor at the end of Oct.

  16. I started the phentermine 4 days ago due to having pcos. I had my cycle about 2 weeks ago I think. I’m on the pill and have at least 2 weeks and 3 days until my next cycle, but today I started spotting. I was just wondering if this is normal. I see in the article above did say spotting between periods.

    • Hi Maegan,
      It is quite common to experience changes to your period with phentermine due to the way it effects your hormones. The spotting you’re experiencing is therefore quite normal on phentermine and nothing to worry about. However, if you experience any changes that concern you or you are in pain or discomfort then be sure to contact your doctor for advice.

  17. Since I started taking Phentermine my period came and it won\’t stop. It has been 2 weeks and 4 days. I used to have regular cycles before Phentermine. I know they won’t say it but there is definitely a correlation between menstrual problems and Phentermine. I am going to stop using it

  18. I started taking Phen on Sept 21st and started my period a few days later. I have always had irregular periods and fertility issues as well as PCOS. It has been almost 4 weeks now and my period has still not stopped. Some days it seems like maybe it is almost over and then nope, back with full force. There is also clotting but no cramps or pain or period like symptoms really. It is super frustrating. Being overweight is hard enough, but dealing with never ending bleeding is even worse.

  19. Yes, I started taking adipex Oct 27, 2016. My period was supposed to start on Nov 1st. I am never late always on time. The last time I had sex I wasn’t ovulating and we used preventive measures. So of course I started to worry but I just couldn’t justify my anxiousness because there is no way I can be pregnant but yet I have still taken 4 different pregnancy tests, and they have all come back negative. So I started researching adipex and found this site. I also had symptoms that I was about to start but nothing…. I also called my doctor that prescribed the adipex and she stated she had never heard of it affecting a women’s period so now I am even more concerned. I am going to wait a couple more days and see if it comes and take another test…..

    • Hi JF,
      Your doctor may not have first hand experience of a patient reporting a change in her menstrual cycle but the forum on this site is testament to the fact that many many women have experienced changes to their period. Your doctor should also know that weight loss itself can affect your period, so it is natural for women taking phentermine to experience changes to their menstrual cycle, if only as a result of the weight loss that phentermine causes. Your pregnancy tests all confirm that you’re not pregnant so there is no need to worry. In fact, the stress of worrying could be affecting your period too, so please just relax and accept this as a side effect that many women have experienced before you. Your period may not come at all this month, so just concentrate on getting a nutritious diet and continuing your weight loss journey.

  20. I have been on adipex for 2 months and am currently on cycle day 80 with no period and all of my pregnancy tests are negative. I went to the doctor a month ago (when I was over a month late) and she did an ultrasound and said the lining of my uterus was very thin and that meant my period wasn’t coming anytime soon. It is as if over night I have no period, no signs of a period coming either. Could this effect my fertility in the future? How long will it take for me to go back to normal after stopping phentermine?

    • Hi Rebecca,
      We’re sorry that your doctor didn’t explain more about why your uterus lining was so thin and in what way that might relate to taking phentermine. Unfortunately we’re not in a position to offer an explanation either as we have no medical training or experience with this issue. You should speak to your doctor again for more information and to find out whether this may affect your future fertility.

  21. I been I phentermine for 2 weeks now and I was supposed to get my period on nov 18 and it didn’t start yet Imma stop taking it for now to see if it will start I long should I wait thank you

  22. I have been taking phen for 1 month. My periods have been regular up until now. I haven’t had a period for a month and I have an increase sex drive with signs of ovulating. I took one test which came back negative. I looked online to see if phen had any side effects to a baby if you become pregnant. Do you have any update on phen and side effects if pregnant??

    • Hi Taylor,
      There isn’t much information available with respect how to phentermine affects unborn children, but it is likely that birth defects, cognitive anomalies and only-onset signs of addiction are all possible effects. This is why sexually active women taking phentermine must use effective birth control. Phentermine can affect your period and sex drive due to hormonal changes so these are quite normal effects and since you’ve had a negative result on the pregnancy test it’s unlikely that you’re pregnant, but in the future you must take steps to ensure that getting pregnant is not a possibility while you are taking phentermine.

  23. I am 38 and have been taking phen for almost 3 months. I have pcos but periods the last 4 years have been regular on their own (huge victory). But since taking phen I spot bleed a VERY dark thick red, almost black, every 2 weeks and haven’t seen a normal period since taking it. I feel nauseous every time I take it so I’ve been taking it every other day instead of daily. I take a prenatal vitamin to try to help with the hormone imbalance but I’m still feeling very weak and also depression has now set in. Anyone else have all or most of these same symptoms, specifically the dark spotting every 2 weeks?

  24. I started taking phetermine (duromine) on the 1st of this month and my period was due on the 5th. I have not gotten it yet but have just started to get the pre period symptoms. I usually have a short cycle of about 20 days and my period always lasts no more than 3 days.

    I have so far lost about 5-6cm all over my body and am down about 4 kilos.

    My mood has actually significantly improved and I did not realize how depressed I was before taking duromine but I noticed such a change in my attituded and energy levels. The effects have been very positive.

    I was getting some pregnancy symptoms such as a metallic taste in my mouth and sensitive to smells. But the pregnancy test was negative. I do not use contraception but I stick to the rhythm method.

  25. Hey😊 I’ve been talking Phentermine now since March 1st of this year. My starting weight was 290 & as of today, my current weight is 197. My monthly has ALWAYS been on point, even while taking the Phentermine. I must admit, Phentermine has not effected me in a negative way at all since day one. Even with my periods. Now, I am 47 & I know I’m close to the BIG ‘M’ approaching soon, lol. Yet, not too sure. My LMP was 11/5. Aunt Florida hasn’t shown up yet but I’ve had some indications. Still, nothing. At this current moment I’m not complaining. My husband would be happy for me to not be PMSing for a bit, lol. Any other people who have taken PHENTERMINE for a few months experience this? As I said, I ain’t THAT worried. Plus, let me throw in here, my husband is fixed, lol. Five kids are enuff, lol! God bless you all!

  26. I’ve been on duromine for 1 month and almost 3 days
    After 2 days of starting duromine I got my period and it went for 29 days straight and had 2 days of relief from it and now it’s started again so in total I’ve had it for nearly 33 days
    I’m constantly tired and the bleeding is not easing off or slowing down
    I don’t know what to do
    I suffer from pcos got diagnosed when I was 16
    But I honestly don’t think this is normal, bleeding for nearly 33 days and only having 2 days relief from it
    Please help I don’t know what to do and I’m over being really tired and feeling sick since losing so much blood

    • Hi Olivia,
      You should speak to your doctor – bleeding for a month straight is very serious and it’s no surprise you are tired as you are probably lacking vitamins and iron in particular after this blood loss. Good luck.

  27. I started adipex on 11-19-16.. as of today 12-31-16 I’m having my 3rd cycle. I take a progesterone only birth control and normally do not have my period. Each time since starting adipex, they have been very painful and mostly clots when I use the bathroom. My cramps are almost unbearable at times. I lost 22 lbs within the first month. I don’t know what to do… I seriously need to lose the weight for health reasons but my period every other week almost is horrible. I don’t know what to do… 🙁

  28. Since I started taking Phentermine back at the beginning of December I have been having a period every other week. It lasts about 5 days and is very dark blood almost black. Then near the end it turns brownish red. I’ll be good for a week then it’ll start all over again the next week. Is this normal? I feel just fine and it feels like a normal period with light cramping. Could my hormones just need more time to adjust?

    • Hi Kristen,
      If you feel fine then this is a good sign but it is probably best to speak to your doctor about these frequent periods to see if there is any cause for concern. Also, you might want to take iron tablets to compensate for this added blood loss.

  29. I was on depo for a year and had my menstrual cycle the week before the shot was due every three months until January. I started taking adipex in August. I lost 15 pounds in 3 months and have lost about 5 ponds in the past three months. I thought the depo was maybe causing my weight gain and preventing me from losing, so I did not get the shot that was due on January 20. I also did not get the menstrual cycle that I expected the week before. So now I am expecting the second cycle and I am cramping and have pms but no cycle. And no more weight loss. I go back to my dr for the 6 month adipex shot next week. I\’m just ready for my body to be healthy and normal again. :/ any words of wisdom for a slightly concerned lady?

    • Adipex check up- not adipex shot. Sorry. 🙂

    • Hello! Thank you for reaching out! Although it is not listed as a side effect of phentermine, anecdotal evidence shows that many women experience changes to their period when taking the medication. We can’t offer you medical advice, you should speak to your phentermine doctor about the symptoms you are currently experiencing.

      While these changes can be very concerning, we hope that knowing that many other women have experienced the same symptoms when taking phentermine helps to put your mind at ease – which is why the phentermine support group such an important source of information and support for many phentermine users.

      Hope that helps!


  30. I’ve always had an irregular period, but since I took phen and lost nearly 35-40 pounds I haven’t gotten my period in almost a year, I stopped phen for about 3 months to hope to get back to regular— nothing. I started open about 4 days ago again to lose some more before summer and I started bleeding, not like period blood I would say though. I am constantly waking up feeling fatigued, dizzy and nauseous. But my question was if I don’t get my period for an extended amount of time due to phentermine could that cause me to become infertile?

    • Hello Stephanie. Thank you for reaching out. Although it is not listed as a side effect of phentermine, anecdotal evidence shows that many women experience changes to their period when taking the medication. We can’t offer you medical advice, you should speak to your phentermine doctor about the symptoms you are currently experiencing.

      While these changes can be very concerning, we hope that knowing that many other women have experienced the same symptoms when taking phentermine helps to put your mind at ease – which is why the phentermine support group such an important source of information and support for many phentermine users.

      In regards to your other question, there is no evidence that phentermine causes infertility. But you should address the issue with your phentermine doctor if you feel concerned about it.

      Hope that helps!


  31. I have pcos and never have a period! but when taking this medication i spot. anyone else have this problem?

    • Me!! Exactly 28 days after starting phentermine I had a 5 day period! (Firstly all black, obviously from old uterus lining, but by the end it was bright red)
      And every month after I had a healthy period again??

      I wasn\’t complaining, cause it gave me false hope that I may be able to have children…

      But after I lost all the weight and stopped duromine, so did my period. It\’s completely gone again.

  32. I started taking phentermine a month ago, my period is always the day before, the day of, or the day after it’s supposed to be here. I’m now 2 weeks late, I’ve taken 3 tests, all negative, I was told my weight could be why I’m getting a negative test. But Idk.

    • Hi Miss,
      The most likely explanation for a negative pregnancy test is that you’re not pregnant. As the article above explains, the majority of women taking phentermine report some kind of change to their period while they are on the medication, so this is probably the cause of your late period. And, as for the possibility of being pregnant, if you are having sex while taking phentermine then you should be extra vigilant about contraception due the potential risks of taking phentermine while pregnant.

  33. I started taking Phentermine on the day my period was due and it still hasn\’t come. It\’s only been about four days. Could phentermine have caused my period to be late on the first day I started taking it?

    • Hello Martha,

      Thank you for reaching out! We can’t offer you medical advice, you should speak to your phentermine doctor about the symptoms you are currently experiencing. Although it is not listed as a side effect of phentermine, anecdotal evidence shows that many women experience changes to their period when taking the medication.

      While these changes can be very concerning, we hope that knowing that many other women have experienced the same symptoms when taking phentermine helps to put your mind at ease – which is why the phentermine support group such an important source of information and support for many phentermine users.

      Hope that helps!


  34. I came here looking to see if anyone else had similar issues. Started phentermine 6 March. As of 3 apr 17. Lost 17lbs. I have symptoms of my period but no period. I contemplated getting a blood test, but if this is common, then I won\’t freak out as much. I was 239lbs now down to 222lbs. Super excited and feeling good!

    • Hi Macia! We are glad you are motivated and happy about your progress so far! However, we do recommend that you consult with your primary physician on any side effects or changes you might be experiencing; only they can assess if further testing will be necessary. Now, also remember that with weight loss, those kind of symptoms are normal in women.

      You can always ask or learn from other phentermine users in our Facebook group!



  35. I started taking phetermine about 3-4 weeks ago & i got my period 3/16-3/25 & now i have it again. This time it started on 4/5 & it\’s been heavier than ever & im having a lot of blood clots as well. I\’ve been to my GYN for my irregular period before taking phetermine & she prescribed me the pill but i was young & my mom didn\’t want me taking it. help!!!

    • We highly recommend that you consult with your primary physician on any side effects or changes you might be experiencing; they can assess if further testing will be necessary. Now, also remember that with weight loss, those kind of symptoms are normal in women.

      And of course, you can always ask or learn from other phentermine users in our Facebook group!



  36. Hi, am a little older then most of your patients however am also taking the weight loss pill. Am too old to have periods but still have all my women parts. Would it be normal to have lower cramps? So no spotting. Just wondering about the cramping being normal? Thank for you time. I hope am not the oldest person on your list(lol). Joyce

    • Hi Joyce, thanks for your comment! We’re not totally sure about this one, so we’d suggest checking with your doctor. Mild stomach cramping is a known side effect, but speak with your doctor if your cramps are not in your stomach, or if they are continuing or severe (regardless of location). Hope you feel better soon!

  37. I don\’t normally have periods due to my birth control, I started taking phentermine Friday and now I\’m having a period. Is this normal? Also when i started my period the phentermine felt like it was dramatically less effective.

    • Hi Samantha, we’d recommend checking with your doctor about this. He or she would probably know best if this is normal or something to be concerned about.

  38. Hi there
    I was introduce to phentermin last year Aug2016. I took the tablet for 3 months in which I lost 15kgs. I would exercise twice a day and eat healthy.
    My period was regular and had no problems. I took a break of three months so I learn to maintain my weight without the aid of this tablet. I succeeded.
    However I\’m looking to loose 10 more KGS. I started the tablet again two months ago but have not been as active in the gym or eating as healthy.
    I got my period as normal on the 1st June. Ended 6th June two days later I started bleedinng again. Almost like spotting on my liner. And have pains almost like I\’m getting my period again. I\’m so bloated as well, my tummy looks swollen.
    Is this to do with duromine?

  39. I started taking Phen on 6/10/17. It initially had me doing all of the right things, when it comes to food. I used to have HORRIBLE cramps, so I have an IUD. I also have a fibroid and PCOS. All of that was to say that I rarely get periods. And when I do, it lasts for maybe two days. I came on my period one week later on 6/17/17. Omg. It\’s like it was before. I\’ve been on for six days, HEAVY cramping and clotting and I want to eat everything. I\’m so confused how this is going to help me with weight loss.

    • Hi Nikki! We would definitively recommend checking with your prescribing doctor about this, especially given your history of related conditions.

  40. I started phentermine on 6/16/17 I\’m now 9 days late on my period when I started it I was already 3 days late I took a pregnancy test at 5 days late and it was negative… I\’m now reading this is normal but would the pill have effected me that fast?

  41. First period day without phentermine and the pain – bleah. I miss the trouble free days. Not sure how but phentermine just made the period pain last 1/2 day – when i still ate everything in sight. Period pain anc cravings were short and sweet – nice.

  42. I started phentermine the beginning of July and I started bleeding the 5th no cramps no pain what so ever. I feel fine. I am passing big clots all through the days and nights. I still excersize, but I am wondering when it will stop or of it will? How do I know if it is helping or hindering? It\’s hard to focus on working out when you have to worry about your period leaking in excessive amount. Anyone have this problem?

  43. I started using Duromine +- 28/06. My period came as usual on the 04/07 but has not stopped. It is not as heavy as my usual period but is concerning as I have never experienced this before. Judging by all the comments this seems to be \”normal\” while on phentermine. Would it be best just to stop taking the pills all together?

    • Hi Jennifer, thanks for your comment! Yes, it is relatively common for women to experience some changes to their periods while on phentermine. However, if you’re concerned or just feel like something is off (you know your body best!), we always suggest checking with your prescribing physician. He or she can help you decide the best course of action going forward. It is not generally recommended to abruptly stop the pills without speaking to your doctor first.

  44. I started Phentermine 3 days ago, and i love it so far, however I was a little worried today when I got a heavy period, which is very unusual for me since I\’m on Mirena and I get very light periods, last one was only 2 weeks ago!
    I figured it had something to do with Phen!
    Does it affect my Mirena in any way?

  45. I\’m on here because I\’ve been on phentermine for less then a month and my period should have started by now. I went to the doctor last week to get birth control and took a pregnancy test which was negative or the doctor wouldn\’t have prescribed the birth control…well I\’m supposed to start the birth control after my period…not sure how to do that if my period doesn\’t come? Should I stop taking phentermine for a few days to let my period break through?

    • Hi Elizabeth! We’d suggest checking with your doctor if you are concerned about your late period. It’s normal for women to report changes in their menstrual cycle while on phentermine (including late and missed periods), but since you’re waiting to start birth control you may want to resolve the issue a little more quickly. It is not recommended to stop or adjust your phentermine without first speaking to your prescribing doctor. Also, make sure that all of your doctors are aware of all of the medications you are taking/considering – it will help them help you!

  46. So I have never got my period before but I\’m 16 and am at the age where I can get it prescribed to me but I was wandering will that damage my body or will that cause me to never get a period or is there anything I should know before taking the drug? Also u should know it\’s pretty normal in my family for females to start our period around 17 actually thanks you

    • Hi Sarah. Phentermine is a prescription medication designed to treat exogenous obesity and it carries the risk of many serious side effects. So, there are lots of things to know and consider before starting this medication and it’s very important to speak honestly with your doctor before taking it. During your appointment, he or she would be better able to advise you on how phentermine will interact with your period and your body. Unfortunately we are not qualified to give medical advice, so we would suggest speaking to a doctor about these concerns.

  47. Is it common if you suddenly stop(not wean yourself off) phentermine to cause your period to be late?

    • Hi Michelle!

      A common side effect of phentermine is its effects on periods. We recommend visiting your primary care physician if the symptoms persist, but it is a known side effect, and happens while on phentermine treatment (remember that phentermine can last days in your body after you stop taking it).



  48. I have an IUD with no period for many years but occasional spotting 2-3 times a year MAX! I started phentermine on 6/18 and dropped 20 pounds in the first month but with that came a full blown period lasting 7 days and have had the same going on my fourth month now. I was concerned so googled and found it does mess with your menstrual cycle but does that include someone who doesn\’t get them because of an IUD? I thought about calling my OB/GYN but because they have been tolerable I figure I have just been fortunate to not have a cycle all this time and to let nature take its course. Would like to know if and when I stop taking phentermine will the periods stop and typically how long after discontinuing use will they stop?

  49. I just started taking phentermine this month, right before my cycle came. Now it has ended (about 4 days ago) and I have been noticing the spotting. I got really worried because, for the most part, my period is regular 6 day and I\’m done. This article was very relieving, but now I\’m wondering if I made the right decision with taking them. I like that I know what to expect, and when.
    And also why is it not a good idea to taking g it if I plan to get pregnant, I mean I\’m not trying to be pregnant this month, but eventually I do and I use no contraception.

    • Hi Nay! The main reason it’s not recommended to take phentermine while pregnant is because these pills help you lose weight, but in pregnancy you want to gain weight. It can be dangerous for baby if mom is losing weight while pregnant. Phentermine may also increase the risk for adverse outcomes during pregnancy. Qsymia, specifically, is known to increase the risk of birth defects.

  50. I started taking phentermine at the beginning of this month (10/04). I was actually about two weeks past due for my period but it’s fairly irregular. Well, eleven days ago, it started. And it hasn’t stopped or slowed. I’m not having any huge amount of clotting or dark blood, like many of the others who have posted, just medium red. Also, it’s not excessively heavy, just a normal medium flow like I would expect in the middle of my usual period. My mood is normal and I don’t feel like I’m having any other unusual symptoms (no cramping, or overeating). My problem is that I would like my period to be over. Like NOW! Any advice?

    • Hi Samantha,

      We suggest consulting with the prescribing doctor immediately. We are not qualified (nor equipped) to provide medical answers, so your case needs to be handled by a healthcare professional (and we think as soon as possible).



  51. I started Phen about a month (haven\’t finish a bottle yet) I been feeling fine except for a \”normal\” fast heart beat from time to time. Lost 2kg so far but now that I had my period, it is longer than normal. I usually have or for 5 days. But I am on my 10th day now. It is a light flow, but enough to be noticeable as a period. When will it stop? Oh, and 3 days prior to my period starting I woke up one morning with a nasty migraine. Is that due to Phen too?

    • Hi Michele! Yes, it’s normal for phentermine to affect your menstrual cycle – including making your period last longer than normal. However, if your flow continues past the next couple of days, we’d suggest checking-in with your doctor. Even though it’s common for phentermine to change your period, it’s still not ideal to bleed for long periods of time. The migraine could have been caused by any number of factors so we’d suggest bringing that up to your doctor at your next appointment, especially if it happens again. In the meantime, you may be interested in our post on common causes of phentermine headaches. Best wishes!

  52. I have been taking Duromine 15mg for 5 days today. I\’m supposed to be PM and haven\’t had a period for 11 months. So imagine my surprise this morning. .Most of the side effects are gone now, so having a period compared to dry mouth, headache and poor sleep is not so bad. Unless it lasts longer than my usual past 3 days.

  53. When I started taking duromine in October my periods were very light then November I didn\’t get my periods and now December am looking forward to my cycle and still hasn\’t come up

    • Hi Dee!

      Phentermine use does affect your menstrual cycle, to varying degrees depending on age, dosage, etc.

      Most users report their cycle going back to normal after they end their treatment, but we always recommend consulting with your prescribing doctor if you have any concerns about any side effects.



  54. I have pretty regular, light periods. I’ve had uterine ablation and tubal ligation done, so no more pregnancies and nice light periods. I had Finished my period about 9 days before starting Phentermine. Literally the next day it started up again and with a vengeance. I’ve been bleeding heavily for 5 days, needing to change a super plus tampon every few hours. Exactly how my periods were before the uterine ablation procedure. I’m willing to put up with it for the weight loss but if it continues I may ask for an Iron prescription since I’m prone to anemia.

  55. I’ve been on Phentermine for 3 months. I had a normal not as heavy period for my December cycle, then shortly after it ended I started spotting now a week before it’s due I’m having another period. A heavy period with clots and all (that’s not unusual). They should make this a side effect because it seriously has me worried:(

  56. I bled the whole time on phentermine (a lil over a month) spotting everyday ruined my sex life! Went to the doctor they ran every test and put me on a 10 day dose of provera which had me bleeding or pouring I should say huge gallons of blood for about 1week and a half (I also quit the phentermine) now my body is back to normal I don\’t think I would\’ve ever stopping spotting/bleeding had I continued phentermine I also learned I had high blood platelets which I\’m sure was connected with the drug . I want to go back for the weight loss results but the side effects are too severe the bleeding ,zombie feeling (blah) i wish I could take it tho

  57. I have been on phentermine for a little over a month now and I\’m on the depo shot. I have a question I don\’t get my period because I am on the shot and now I still haven\’t gotten it but I bleed during sex. I

    • Hi!

      Phentermine has been known to affect the menstrual cycle of patients (like the quantity and frequency of bleeding). You could consult with your prescribing doctor, but it’s a relatively common side effect and your cycle and any abnormal behaviour should go back to normal once treatment ends.



  58. Haven\’t had period since uteran ablation in 2011 been on adipex a week today and have bleeding and period cramps??

    • Dear Suz,

      Phentermine has been known to affect the menstrual period of women taking it. You will see either decreased or increased blood flow, but it should only last until the phentermine treatment is over. For any other questions concerning this side effect, we recommend you consult with your prescribing doctor or your OB/Gyn.



  59. I had abalation about three years ago. The first year NO MENSTRUAL. I was super excited because my periods were so bad I had become anemic. Then after the first year I started with light little puffs of period just enough for a panty liner, but very irregular, maybe every 3-4 months. I started the phentermine in October 17. My doctor prescribed them for 4 months on hopes to loose some initial weight to ease my back pain to help me get into an work out routine. I dropped 20 lbs even during the holidays. I\’m only my last bottle this month and have had a menstrual all month, only a day or two heavy, but some dark bloody discharge all month, I also noticed hair loss which I have a thick head of hair any how. I also lack sleep, I do have dizzy spells. I can go all day despite my better judgement without eating a bite or drinking water. My mouth is like cotton. I take my last pill this morning. My insurance company will only allow it for a short time. After about 20lbs. I kinda plateau. Hopefully now that I\’m finished my body will go back to normal. I\’m going to start doing yoga and Pilates despite my still constant back pain. I just hope to maintain or kick the weight loss back in with exercise and healthy diet for my son\’s wedding next month. Momma gotta look good on the dance floor! Best wishes to those using it, just don\’t abuse it. I do believe over an extended period it can turn harmful. Oh I forgot to mention depression. One more reason to really pay attention to what the medicine is doing to you. I do not feel any jitter or increases in heart rate, but hardly no sleep what so ever, yet I feel exhausted, does anyone know how long after coming off of it your body will regulate and if I should do anything to promote it to regulate?

  60. I am in my 3rd month of taking phentermine. I have lost 15 lbs which is great, but the 1st month and the 3rd month i have started spotting a week before my period is due and end up having a 10 day period. I am on an oral birth control pill that has always made my periods regular always starting in day 23 and dine by day 28. I\’m definitely not a fan of the early spotting and feeling like I\’m having my period every 2 weeks while on the pilll even. Is it normal to have spotting on phentermine while on oral birth control too?

  61. I started phetermine on 4/3/18 I have lost 11 lbs. I am currently using nexplannon birth control and have never had a period with it but since I started taking phetermine I am now experiencing spotting and some light bleeding and cramping. This would be my normal period time so I assume all is normal.

  62. Hi, i started Phentermine when my periods started. And since then it is being a month i have not stopped my periods. No cramps no pain but it is regularly bleeding. I had an untradound and an expert gynae opinion but they said i have everything normal. My thyroid was normal my cycles weee normal but its like irritating now since i am bleeding i stopped phen for a while but the bleeding isnt stopping. The medicine is not registered in my country but as i am a doctor myself so i asked a friend to send it to me from uk.

  63. I took phen about 3 yrs ago no prob. I started back in middle of feb and since then every 2 weeks, for over 2 weeks, i have had menstrual bleeding. I have gone to my obgyn in hopes to find the issue. Blood test and thyroid is normal. Only explanation is the pills. I have lost 25 lbs so far but i can not continue to use these pills if this is the emotional and physical burden they will cause me. Light spotting that turns into heavy, brighr, blood cloths. Would lowering the dosage help?!

    • Hi Tia! We’re sorry to hear about your abnormal periods 🙁 We would recommend speaking with your prescribing doctor to see if he/she thinks lowering the dose would help. He or she is a medical professional, and more familiar with your specific case/medical history, so he/she would be better able to assist you in working through this reaction. Best wishes!!

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