Home > Blog > Will Phentermine Show Up On A Drug Test?

Will Phentermine Show Up On A Drug Test?

drug test

One concern for many people taking phentermine is that phentermine is said to give a false-positive result on an employment drug test. In response to the many questions we’re asked about phentermine and drug tests, here we explain more about the drug screening process, why phentermine can give a positive result, and how to avoid this causing problems with your employer.

What Does The Drug Test Look For?

Drug testing is an action that an employer or prospective employer can take to determine if employees or job applicants are using drugs. Rather than acting as a test of impairment or whether recent behavior is as the result of drug use, employment drug tests are implemented to create a safe working environment for all employees. Workplace drug testing aims to deter employees or potential employees from taking drugs, to be able to identify and help employees with drug and/or alcohol problems, to protect the general public, and to comply with employment laws and regulations. The most common method of drug test is urinalysis, and will most typically test for five categories of illegal substances. Known as a 5 panel drug screening, this test looks for evidence of THC, Opiates, PCP, Cocaine, and Amphetamines.

In the event of a positive result in both the initial and confirmation tests, the medical review officer (MRO) then reviews the results and contacts the individual to make sure that there are no medical or other reasons for the result. It is only at this point that the MRO may report the results to the employer. Certain medications can cause a false-positive result on the drug test. If this is the case and the employee can verify that he or she has been prescribed the medication and is taking it as instructed then the test is reported as negative.

Keep reading, or check out the infographic below, to learn more about phentermine showing up on these exams.

Will Phentermine Show Up On A Drug Test?

Although phentermine is not an amphetamine, its chemical structure is similar to that of amphetamine, meaning that phentermine can give a false-positive result for amphetamine in a 5 panel drug screening urinalysis. However, following the information above, with evidence of your prescription from the doctor who prescribed you phentermine, then the result should be declared as negative. A key factor is that you have to have been taking it as directed, so this is another reason to be sure to follow the prescription and not to take more than directed by your doctor.

drug test

If you have been taking more than the recommended dosage then excess levels of phentermine might raise questions for the MRO reviewing the positive result. Although phentermine is not an illegal drug, it is controlled substance, listed on page 12 of the Drug Enforcement Agency’s January 2016 List of Controlled Substances, and can only be legally obtained by prescription. If you cannot provide a prescription to explain the presence of phentermine in your system following a drug test then this would be considered illegal usage and the MRO may insist that the positive result stands.

If you know that your employer may request a drug test during the duration of your phentermine prescription then in some circumstances it may be better to inform your direct supervisor that you are taking phentermine and to provide proof of your prescription before a drug test. This will avoid you having to retrospectively disclose that you are taking phentermine and the possibility of a false-positive reading being declared to your employer.

How Long Does Phentermine Stay In My System?

Due to confusion between phentermine and the now banned weight-loss medication Fen-Phen, as well as a general misunderstanding of what phentermine does, many phentermine users choose to keep phentermine a secret. Therefore, it is not surprising that some people may prefer not to disclose that they are taking phentermine to their employer. To avoid the possibility of a false-positive result, if you are aware that you will have a drug test soon then you may prefer to stop taking phentermine for a few days. We are often asked how many days phentermine stays in your system, and although this varies depending on the person and their urinary pH, the medication has a half-life of about 16-31 hours under normal conditions. So, phentermine should not be detectable in the urine after a period of around four or seven days. It may, however, be detectable for longer if you were taking more than prescribed or used phentermine for a long time.

If you’re concerned about a false-positive result on a drug test due to phentermine then another option is to take a phentermine alternative such as Phen Caps instead of phentermine. Phen Caps will not show up on a drug test as they do not contain ingredients similar to amphetamine, so you can benefit from the appetite-suppressing effects and energy boost without the worry of failing an employment drug test.

Have you received a false-positive result on a drug test as a result of taking phentermine? Let us know your experiences by commenting below.

109 thoughts on “Will Phentermine Show Up On A Drug Test?”

  1. Avatar

    I have taken a few drug test over the period of 2 years Both pre employment and random. 2 times I was on phentermine. Both times they never raised questions. In my opinion, if you take it as directed and have a prescription for it, you should be okay. Some companies have a list of prescription drugs that they ban from any employee using while at work. So weather or not you have a prescription they can legally terminate you as long as they have a contract or employee handbook signed by you stating you read and agree with all in the book. Some people choose not to read those and when it comes to being fired they claim they didn’t know. Hope this helps you out. If you have any concerns about what you can take while at work, simply ask for the list of drugs that banned from your company.

  2. Avatar

    I have taken 3 drug tests in the months I’ve been on Phentermine and all 3 have come up positive for amphetamines. I’ve never taken a “real” amphetamine in my life. There are many medications that can cause false positives for many different drugs (Tylonal, Benedryl, anti-depressiants, etc), but these false positives happen few and far between. From my experience, I’d say you can almost expect to come up positive for amphetamines on the initial urine test if you’ve taken Phentermine within the past few days, but I’ve never had it tested further with GC/MS.

    1. Avatar

      Hi Nana, yes – it’s possible it will. Be prepared to show your prescription just in case.
      Rachel, phentermine.com

    1. Avatar

      Hi Alex, the chances are pretty low. Although it can vary depending on the person, phentermine should not be detectable in the urine after a period of around four or seven days
      Rachel, phentermine.com

  3. Avatar

    I had taken phentermine a week ago then off for a week, then I took one on Saturday, today is Sunday. I will have an upcoming drug screening for new employment this week. Should I worry about it showing up? I am prescribed by a doctor but I would rather not have my new employer know reguardless.

    1. Avatar

      Hi Sarah! That’s very understandable. Although it can vary depending on the person, phentermine should not be detectable in the urine after a period of around four or seven days, but will likely show-up if you take a drug test before that. So depending when your drug screening is this week, the likelihood varies. Regardless, be prepared to show proof of prescription in case there are signs of amphetamines in your system.
      Rachel, phentermine.com

  4. Avatar

    I took a phentermine Tuesday I took a random drug urine test today (Friday) I’m so worry if be coming positive?

    1. Avatar

      Hi Mary. Although it can vary depending on the person, phentermine should not be detectable in the body after a period of around four to seven days, but will likely show-up if you take a drug test before that. So, be prepared to show proof of prescription in case there are signs of amphetamines in your system.
      Rachel, phentermine.com

  5. Avatar

    I have a valid prescription for phentermine and am prepared to bring my medicine with me to the lab in the morning as proof. However, as I was reading the comments I saw alot of questions about taking 1/2 A day … I am on 2 daily – is there a level that is considered a “pass” or “fail” with a prescription? Or are they just concerned with ensuring you are taking them legally? I was thinking I wouldn’t have any delays or issues but I didn’t realize people took such varying amounts.

    1. Avatar

      Hi Genny, thanks for your comment! We can’t speak to your company’s specific policies, but in general drug tests are given to determine the presence of illegal substances in your system. So, if you have a valid prescription you should be okay – regardless of your prescribed schedule/dosage. Often times people that take one pill per day are on a higher dose pill (e.g. 37.5mg), while those who take phentermine multiple times per day use lower dose pills. To learn more about different phentermine dosages/schedules, check out this page.
      Rachel, phentermine.com

  6. Avatar

    I take phentermine I have for a long time this is the first time I tested positive for amphetamine. I take losartan metformin Gabapentin and Zantac when their doctor called to ask me about my prescriptions I told him which ones I had and he told me that none of those could test positive for amphetamine and my job is now on the line I have been suspended

  7. Avatar

    I’m perscribed phentermine 37.5 mg daily & have taken as perscribed for approximately 3 months daily. As I lost my desired weight I started to taper the phentermine approximately once to twice a week for approximately 1-2 months. I’ve taken ABSOLUTELY NO phentermine for over a month (I actually believe 2 months. But not 100% sure). I took a pre-employment drug screen with a false positive amphetamine result! I now have to share my phentermine prescription with my potential new employer! Imagine my SURPRISE & EMBARRASSMENT! I wasn’t prepared for my explanation because I’d forgotten all about taking the medication (it had been so long). I really don’t understand why it showed up in the slightest.

  8. Avatar

    That is surprising. I’m wondering if it showed up because u took them for a while? I may have had 3 in my life. 2 over 90 days ago and one 28 days prior to my test. Guess I’ll find out when I return in 3 months.

  9. Avatar

    Hi, I have been on phentermine for 3 months. we all get dropped regularly at work because of the work we do. On random 5 panel tests and on ones sent to the lab, neither have come back positive for amphetamines, which is great! It also makes me wonder though after reading all these posts. I have lost 34lbs, which is even more awesome, but why is it not showing up, if others do? I take my pill every morning before I leave for work at 5am. What are your thoughts on this? Could I be getting fake pills from my doctor?

  10. Avatar

    I’ve taken a dope 37.5mg for 2 months,my last one was taken a week ago.I test weekly and it’s never shown up,but I’ve also let them know and see my script. However my primary doctor tested me two weeks ago sent it to lab and found it…she was upset because I’d went to another doctor/dietician to get them as she refused to after a script of one month.She told me if I tested positive again she’d stop all my other meds which are all non narcotic.Im very upset as she is trying to tell me I cannot see her if I see other doctors.Shes only a practicioner.Is she breaking medical laws?I pay all out of pocket to see my dietician.

    1. Avatar

      Hi April – Your doctor may be concerned about the possibility of dangerous drug combinations if you’re receiving prescription medications from different physicians, especially when she specifically refused to prescribe phentermine. She may also be worried that you’re still taking phentermine if she had a specific reason for halting your prescription. So, we would suggest speaking with her about your phentermine use (both why she doesn’t want you to take it and why you do want to take it) to see if you can reach some sort of mutual understanding. Best wishes!
      Rachel, phentermine.com

  11. Avatar

    I recall years ago when I was under a doctor’s supervision while taking Phentermine, I was unexpectedly rushed to the hospital due to an allergic reaction from an insect bite (not Phentermine!). My urinalysis tested “positive” for the drug and I recall the nurse telling me “we have a problem” meaning the Phentermine had shown up in the test. She questioned me and I told her I was taking it under a doctor’s care. She didn’t go any further by asking me to provide proof from the doctor, but I supposed she could have. So I would say if you are taking it, yes it will be a “red flag” to a prospective employer unless you prove it is legal. If found illegally, you probably could be fined or arrested. I know it sounds ridiculous, but the law is the law. So if you take a drug test, be aware the test WILL find this substance.

  12. Avatar

    I don’t see why there would be a problem with pre-employment drug screening if the medication is prescribed. I was screened for my current job and many times prior as required by all facilities when I was going to college and never had a problem. They used a 12-panel drug screen. I was taking phentermine, tramadol, and ambien (not all at the same time). I never received a call to verify my scripts but now there is registry for all controlled substances that a provider can access to determine what meds have been prescribed, by which doctor, which pharmacy filled the script on what dates, and the exact dose prescribed of all meds filled in the past 12 months. I work in healthcare and have easily verified scripts with this system to determine if the patient has the med prescribed or is using illegally.

  13. Avatar

    I was taking Phentermine 37.5 , for about 1 week ( skipping 1 or 2 days through out ) . I then took a urine test , which tests for 17 different illegal drugs and parscription.medsp .
    I hadn’t taken the Phentermine from Sunday @ 11 am, to Wednesday at 4 pm …. So, about 77 hours off them. I’m worried , Yes I have a script but I do not want it to show up or have to explain. I obviously will, if needed . Amphetamines are cleared from urine, in about 3 days . Is there a difference with the Phentermine and the amphetamine that way ( I’ve saw it saw ” 4-7 days for phen” ) .

    1. Avatar

      Phentermine can indeed take up to 7 days to flush out of your system. There’s no hard, fast rule about how long it takes because it varies, depending on factors such as time under phentermine treatment, age, etc.

      We hope everything turns out right!



  14. Avatar

    I was taking Phentermine 37.5mg for about a month or 2. Since then I was put on Probation and they asked me to stop taking it due to a positive amphetamine panel in my urine. I havent been taking it for a whole month now and its still showing up in my urine. This past week my amphetamine level even spiked up and I honestly haven’t taken not one dose. Why is it that this is happening?

  15. Avatar

    I just need to know if this 30 mg phentermine will show up in a hair test as I don’t have a prescription For it I been taking one a day to lose weight for about two weeks and I just got called today for a job on a rig and they do hair test now I’m worried

    1. Avatar

      Hi Rudy. Yes, it’s very possible that the phentermine would show up in a hair test if you have been taking it everyday for 2 weeks.
      Rachel, phentermine.com

    2. Avatar

      What happen with your results? I’ve been off phentermine for 2 months and have a hair follicle and I’m worried. I don’t have a script for it.

    1. Avatar

      Hi Jim, yes – phentermine is chemically similar to amphetamines, so taking any amount of phentermine may result in a positive drug test. If you take more than prescribed, it is more likely to show up for longer. Be prepared to show your prescription just in case.
      Please note: for safety reasons, you should NEVER take phentermine more often, or at a higher dosage than prescribed by your doctor.
      Rachel, phentermine.com

  16. Avatar

    Hello will phetermine pill show up on mouth swab test. My last pill was yesterday at 10 am .. i have drug test today at 1

  17. Avatar

    Hello I took axcion phentremina from Mexico with a prescription from there. I took it for about 8days. I will have a drug test some time next week. Will phentremine come up as a positive after being off it for about 12 days?

    1. Avatar

      Hi Jay! It probably won’t show-up in your urine, but it may still show in other forms of testing. Either way, be prepared to show the prescription since speed of metabolism & elimination varies between people and depending on a variety of other factors.
      Rachel, phentermine.com

Leave a Comment

Your email address will not be published. Required fields are marked *

Scroll to Top