How To Combat Constipation On Phentermine

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Constipation is one of the most common side effects of phentermine. As well as being painful and embarrassing, it can really slow down weight loss too. Here we explain more about constipation on phentermine, including why it occurs and the best ways to combat this side effect.

What Is Constipation?

Constipation is a problem that many of us have suffered from at some point in our lives. Being constipated means that bowel movements are difficult or happen less frequently than normal. Causes can include a change in routine, stress, and some medications, or it may be a sign of an underlying health issue. However, most cases of constipation are not serious and often resolve themselves within a few days.

Many people think that you should have a certain number of bowel movements per day or week, but the truth is that everyone is different. While some people go three times a day, others will only go three times a week. It’s common to have one bowel movement every day but however often you go is considered normal for you. It’s not a problem to go a couple of days without one as long as you feel fine. But, fewer than three bowel movements in the space of a week indicates that you’re constipated. And if it’s less than once a week then it’s severe.

As well as problems passing stools, constipation can result in a swollen abdomen, stomach pains, nausea and vomiting. It also means that you are not releasing the build-up of waste in your body, so you may feel bloated and gain weight.

Why Does Phentermine Cause Constipation?

Like amphetamine, phentermine stimulates the nervous system and leads to dehydration. This is why other common phentermine side effects include dry mouth and headaches as well as constipation. Dehydration causes you to become constipated as there is not enough water in the body available to help expel waste products through stools, which are typically 75% water.

Constipation has also been linked to low mood and stress. Therefore, some of the other side effects of phentermine, such as depression and anxiety, may also contribute to constipation,. Furthermore, many people taking phentermine experience strong appetite-suppression and eat a lot fewer calories than they used to. This drop in food intake may then cause the digestive system to slow down, resulting in constipation. This is especially likely if you’re not eating a balanced diet or you’re limiting the intake of certain food groups.

How To Combat Constipation On Phentermine

If you’re usually regular as clockwork then going a day or two without a bowel movement might have you reaching for the laxatives. However, it’s best to try more natural methods first, especially as these can also help to boost phentermine weight loss. Here’s our top ways to beat constipation on phentermine:

1. Drink More Water

Even before you experience side effects such as dry mouth and constipation, you should up your water intake in anticipation of the dehydrating effects of phentermine. Water boosts weight loss too, so it should always be part of a healthy lifestyle. As a general guide you should drink eight glasses of water a day, equivalent to 2 liters or 68oz. If you start to experience constipation then drink two to four extra glasses of water each day.

Many people also swear by a glass of warm water with lemon in the morning. Warm water increases the tightening of the intestines, which then facilitates bowel movements. The lemon helps as its high acid content stimulates the digestive system to get things moving.

2. Avoid Dehydrating Drinks

While you’re drinking more water you should avoid drinks such as coffee, soda and alcohol. The high sugar levels in alcohol and soda make constipation worse, while coffee is very dehydrating. Although caffeine can be considered a quick fix for constipation, it is also a diuretic, meaning that it takes moisture out of stools, making them very painful to pass.


3. Add More Fiber To Your Diet

If you’re following a low-carb, high protein diet, this might also be causing your constipation on phentermine. General advice for combating constipation states that you should limit high-fat low-fiber foods, such as meat, cheese and processed foods, and eat more fiber-rich foods, often found in carbohydrates.  Women need 25g of fiber per day while men need 38g. But, not all fiber is created equally when it comes to our digestive systems. Soluble fiber slows digestion and boosts metabolism, but it’s the insoluble kind of fiber that helps to facilitate bowel movements. You can find insoluble in fruit and vegetables – especially in the harder-to-chew skins (e.g. cucumber, peppers, apples), wheat bran, and whole grain versions of products such as cereal, bread, pasta and rice. So, for the sake of your digestive system, remember to eat healthy carbs as part of a balanced diet.

4. Get Some Exercise

Inactivity is known to make constipation worse, so getting some exercise is another way to promote healthy bowel movements. While moderate to rigorous physical exercise is preferred, just going for a quick walk around the block will help. Plus, you’ll reap the added benefits of exercise as well as faster weight loss!

5. Reduce Stress

Since depression and stress can trigger constipation, the way phentermine can lower your mood may also affect you this way. Worrying about constipation and stalling weight loss may then cause added stress and worsen symptoms. Reduce stress through yoga, meditation, these stress-management techniques, or get a soothing massage. Massaging your abdominal region in particular relaxes the muscles supporting the intestines, helping you become more regular.

6. Try Prunes

No it’s not an “old wives’ tale”, prunes really are powerful when it comes to constipation. Prunes, or dried plums, are rich in insoluble fiber and contain sorbitol, which acts as a natural laxative. Eat 6-12 prunes per day to see if this helps resolve your constipation. Or, if you prefer you can drink 4-8oz of prune juice in the morning to stimulate a bowel movement.

7. Choose A Mild OTC Remedy

If those methods don’t help, you may want to use a mild over-the-counter stool softener such as Colace. This can be purchased with or without an added laxative. Or, a laxative such as Milk of Magnesia can help promote a bowel movement. This should work in around 4 hours and is stimulant free so you won’t suffer from cramps as a result. Lastly, several members in our Facebook support group have also recommended magnesium citrate, which can be taken as a liquid or in pill form. However, this product is very strong and can be extremely fast-acting. Therefore you should take great care and never exceed the dosage advised.

Please be aware that stool softeners and laxatives should not be taken for more than two weeks. So, if you are experiencing ongoing problems with constipation on phentermine then you should consult your doctor.


Are you experiencing constipation on phentermine? Do you have any tried and tested advice to resolve this side effect? Let us know by commenting below.

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35 Responses

  1. I have loss 10 lbs in a month…no constipation…thus actually has helped my IBS…I feel normal and my stomach isnt hurting or gurgly every day.

    • Are you sleeping at night? I lay awake and have to take another just to make it through the next day and have been constipated from day one…

      • I\’m taking 37.5 mg tabs and I take it between 7am-8am, this has helped me be able to get to bed without a problem with sleeping. I would look at how much activity you\’re getting in a day; if you\’re not physically active, sleep may be a problem. I had to limit myself to one cup of coffee in the morning because more than that was making me too hyper. Make sure you\’re not taking in any additional caffeinated products. Hope this was helpful.

    • Oh my gosh. You were the first person that I’ve heard taking phentermine and it has helped your IBS. I too went to my doctor and said phentermine causes constipation which is what I need. Doesn’t constipate me it makes me normal. Or if I’m going to have a bout of diarrhea, I can make it to the bathroom when I’m on phentermine. Thanks for sharing. Karen

    • Since June I have lost about 50lbs. And it has helped my Crohn\’s.

    • I\’ve lost 6 pounds in 3 weeks. I\’m doing a hour of cardio and weight training. I use melatonin at night just in case I have sleep issues. I drink about a gallon of water a day . I\’m super constipated . So I\’m going to purchase stool softeners. I\’ve tried laxatives. They make my stomach hurt and when I go its beyond loose and then I\’m right back to being constipated again.
      Good luck to everyone on this journey .

  2. Dandelion root, milk thistle and coconut oil

  3. Also green tea.
    I have been on phentermine for a month now. I have lost about 14 lbs which is wonderful!
    I am a person who literally has at least 3 bm’s a day. I immediately began to cease having any but one very little every few days?
    The remedies I recommended have always kept me very regular and I am starting back on all three as I have only been taking the milk thistle. I would say the dandelion root is most effective. I had to stop taking it previous to starting the phen because it cleared me out continually. I am thinking it will be just about right with the phen. Also, I have experienced extreme dry mouth and I am constantly drinking water all through the day

    • Bonnie, please, this constipation from taking phentermine is kicking my butt. I need something that is safe to take while on phentermine because otc laxacitives can only be taken for two weeks. Ive lost 16 lbs but im so miserable cause i cant go. is my email addy.

      • Use MiraLax, it\’s a non stimulant laxative and it can be used twice per day. It simply pulls more fluid into the colon so it make the stool easier to pass.

  4. I have been on phentermine for about 2 and half months. Did very well with weight lose I went down from a 22 to a size 14 now and a total of 33 pounds. But the last few weeks has been very bad I got very bad constipation with phentermine so I have taken myself off the last few days and feeling better now but I had bad stomach pain too. I might try it again in a few weeks I hope I don\’t gain the weight back but I do walk anywhere from 4 to 6 miles a day and no sugar or carbs I felt full and no cravings. Did anyone else have it this bad too and what did you do about it to help?

    • I have been on since Feb 8th 2017 I have lost 34 lbs it\’s slower then I wanted to lose the weight but 34 lbs is still a good loss and I have been experiencing a bit of constipation
      As of lately and I KNOW it is because I have decreased my water !!! But I am now back to upping my water. My weight loss has stopped ! I have plateaued I\’m at 198 & I can\’t lose any more so I am now kicking it up again with the excercise and measuring everything I am eating in also putting much more fiber in my diet !

  5. I have been on Phentermine for a month and have lost 12 pounds. I went to my Dr and he was very proud and so was I. But, I have had constipation and I use docolace ,100 MG …. ,2 at a time as needed and it helps. Don\’t forget to drink water, water, and water !!!!

  6. I\’ve been on phentermine since March 23 and have lost 18lbs. Occasionally when I don\’t stay focused on drinking enough water, I get terrible constipation. I like the senna-based tea, Smooth Move. Drink it before bed, and when you wake up you should have relief without cramping.

    • Thanks for sharing i will try senna tea leaves before sleeping…imb1 wrrk on duromine 15mg constipated after drinking coffee

  7. I think it constipated me too….besides the dry mouth, headache, thinking in my head way too fast, can\’t sleep till 1am….i take the pill at 7am or 8am so I\’m not sure why it\’s lasting so long on me to wear off …..and the first 2 day I lost 5 lbs and the 3rd day went a pound up ….which is weird fue I barely ate.

    • Hi Liz, thanks for your comment! If you are relatively early in your phentermine prescription, these side effects may be affecting you more now and should eventually lessen with time (if not, check with your doc). It’s normal for body weight to fluctuate a little bit day-to-day, so don’t worry too much about one pound here or there as long as you are trending down overall. Still, make sure you are eating enough to fuel your body – it will actually help you lose weight faster! If you’re interested in reading more about this, check out our article here!

      • Try melatonin 5mg

    • Have you considered Lowering your dose. You shouldn’t be having head aches or feeling like you had too much coffee…..

  8. I just started the adipex. 8lbs my first month. Constipation got so bad I had to resort to suppositoryou enema. Not proud of that but it definitely worked

  9. Thanks so much for this information. Had no idea constipation was a side effect. I suffer from IBS. My regular Dr. Was out of town and the Dr I saw last week put me on adipex. He never mentioned it. Considering what I read about dehydration and the fact I also take lasix, this would have been nice to know. I haven\’t pooped in about 3 days. I manage my IBS closely and was trying to figure out what foods ect. I had eaten. I then thought about the adipex. I googled it and found this site. I are prunes last night and feel better. However, the bowel movements came with terrible abdominal cramps. Almost like when I am not monitoring my IBS. So…lots of water, and prune juice for me from now on.

  10. I’ve been taking phentermine as well at topimarate since October 18th and have lost 27 lbs so far yay!! Although this entire month has been a bit of a struggling plateu unfortunately. I can’t help but wonder if it’s due to my constipation increasing. In the beginning it was a welcome side effect due to dealing with IBS type situation prior to taking them. But this month has been worse and I’ve now gone a week without a BM. TMI I know. I’m thankful for everyone’s suggestions and will try some of them out and definitely will be increasing my water intake. I realize now that I’m definitely not drinking as much water as I probably should be.

  11. I have been taking Phentermine for two months. Was 257. Now 242. I am happy with the gradual loss. The first 4weeks constipation was a huge problem. I started adding benefiber to my coffee each morning, and to an applesauce or Activa yogurt cup every day. So that\’s twice a day, as reccomended by my GI Dr. -Big improvement. He also suggested drinking liquids with anything in it(Gatorade, fruit juice, ect), to stimulate the GI tract, in addition to the water increase I was already doing. I also take phentermine \”breaks\” on the weekends. My appetite has definitely decreased. No other side effects at this point.
    My PCP, monitors me every month. After the 3rd month he will have me off of it for a while. I like his close monitoring approach. 🙂

  12. I have been taking phentramine for 11 days. 6 pounds down! On the other hand, for two days now I have had the most horrid stomach cramps and pain in my abdomen. Obviously, I start googling. Find out constipation can do that. I wasn’t drinking enough water. So kicking that up. Thanks for all the help. I just want these stomach pains to go away.

  13. I was on phentermine for 2 months and only lost 5lbs. It helped me kick my sweets cravings keeping me from becoming diabetic. Otherwise I really haven’t seen the results like others have mentioned. I have sever constipation and stomach bloating/pain. I feel like my digestive system has just stopped working. I have tried MiraLAX and, Colelace. I really hate adding drug after drug to my body on top of everything else. I will try some of the suggestions above.
    Can anyone give me an idea of what your daily food intake looks like? I know I’m not exactly eating the right foods but I’m certainly eating a lot less. However, I wonder if that has just shut down my metabolism and this doesn’t work for me.

  14. My Doctor prescribed 37.5 mg Adipex and said to take a half tablet in the morning. She also put me on an 800 calorie diet. Has really made me rethink how I eat. I’ve lost 12 pounds in 3 weeks and I feel fantastic. No sleeping problems or headaches. But the constipation is real (ugh). Just started adding flaxseed to my yogurt, so we’ll see how that goes. The pharmacist also told me to take it early in the morning and wait a half-hour to 45 minutes before I eat. I take mine at 6:45am

  15. I stasrted taking phentermine about a week ago and I went With out eating for about 3 days have me horrible stomach pains still get a little stomach discomfort I add A stool softener to it because I already have problem going regularly and I don’t want Constipation but I dont Know if I have Enough in my system to go since I went So long without eating. I’m gonna increase my water intake was t drinking enough and I add Lemon to it also hope this helps.

  16. I\’ve been taking phentermine for about 2 weeks now. I\’m down 8lbs, but I\’ve had 1 bowel movement since I\’ve started taking it. I\’m drinking water all day, but that hasn\’t helped. I have to go, I just can\’t. It hurts. Not sure if this is worth the weight loss or not.

    • Hi B! We’d suggest that you talk to a doctor about this. A little constipation is normal with phentermine, but yours sounds pretty severe. Your prescribing physician can suggest some options to help you go, as well as assess whether adjusting your dose or switching medications would be a good option in your case. Hope you start feeling better soon!

  17. I have been on Phentermine for 6 weeks today, and I am down 25 lbs exactly. Wish it was more, but I guess I can\’t complain. I am just beginning to feel a little constipated. I\’m still going every couple days, but it is very painful and causes bleeding. I know I am not drinking enough water, but I also think I am just not eating enough to make me have to go more often. I am taking in fewer than 20 cabs a day, and normally around 500 calories.

    • Hi Donna, congratulations on your weight loss so far! Yes, it’s very important to stay hydrated and eat enough while taking phentermine.

      Aim for at least 8-10 glasses of water per day, or choose hydrating foods (like soup, watermelon or grapes) – enough so that your urine is a light yellow color. Drinking enough water should help soften your stools. You’re also correct that you’re also probably not eating enough. Try to hit a minimum of 1200 calories per day while taking phentermine. Eating a lot less than that makes your body feel like it’s in starvation mode and actually prompts it to hold onto fat more. If you don’t have much appetite, try adding in a couple of meal replacement shakes — they’ll provide both hydration and calories to hopefully help you feel better.

      Best wishes!

  18. I\’ve been on my phentermine for about 2 weeks. My constipation just started this week. I usually have a bowel movement every day at least sometimes two. I am also on the keto diet as well. What should I do to assist with the constipation? Should I stop doing keto as well?

    • Hi Kanesha! The phentermine may be causing constipation, but your keto diet may be making it worse – depending on what you’re eating. Regardless of your chosen plan, it’s important to include plenty of fiber and stay well-hydrated to keep things moving. Fiber typically comes from whole grains, beans, fruits and veggies. If you’ve largely cut these items out of your diet with keto (and only eating low-fiber foods like meat and eggs) or not getting enough water, that could be worsening your constipation. Hope you feel better soon 🙂

  19. Im taking just half a dose of the 37.5mg due to blood pressure issues. I have been horribly constipated from day one. I went over 2 weeks without a bowel movement and spent a weekend taking some laxatives, and did have some movement, …now its been another week and a half and no bowel movement again…nothing is working, more water, fiber etc…Im starting to feel very tired and sluggish and moody…..I dont even have the urge to go to the bathroom..

    • Hi Anne, we’d suggest that you talk to a doctor about the constipation ASAP – especially since at-home remedies aren’t working and it seems to be getting worse. Hope you get some relief soon!

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