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 these causing problems with your employer.

Keep reading, or check out the infographic below, to learn more about phentermine showing up on a drug test.

What Does The Drug Test Look For?

The most common drug test method is urinalysis, which 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.

Drug testing is an action 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 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, identify and help employees with drug and/or alcohol problems, protect the general public, and comply with employment laws and regulations.

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 ensure 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.

Will Phentermine Show Up On A Drug Test?

drug test

Phentermine can show up on a drug test as a false positive for amphetamine. 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 your phentermine, the result should be declared 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.

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 a 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 Your System?

Phentermine should not be detectable in the urine after a period of around four or seven days. Although this varies depending on the person and their urinary pH, phentermine (Adipex) has a half-life of about 16-31 hours under normal conditions. It may, however, be detectable for longer if you were taking more than prescribed or used phentermine for a long time.

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, you may prefer to stop taking phentermine for a few days.

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 worrying about failing an employment drug test.

Frequently Asked Questions

What is the half-life of phentermine?

The half-life of phentermine is around 16 to 31 hours. However, the drug’s half-life will vary depending on each person’s metabolism and the pH of their urine.

How long does phentermine stay in your urine?

Generally, phentermine will no longer be detected in the urine 4 to 7 days after the last dose was taken. However, the detection period could be longer if phentermine has been taken at a high dose or for a long time.

What does phentermine show up as on a drug test?

Phentermine can show up on a drug test as a false positive for amphetamine. This is because, despite being different drugs, phentermine and amphetamine have a similar chemical structure.

If you can provide your employer with evidence that phentermine has been prescribed for you, then a positive result for amphetamine should be declared a false positive.

Can I get fired for taking phentermine?

If you take phentermine without a prescription, your employer may view this as illegal usage of the drug. This could result in disciplinary action.

Phentermine is not illegal, but it is a controlled substance. This means it should only be taken if you have a prescription.

Will phentermine show up on a military drug test?

Phentermine may show up as a false positive on a military drug test as it might register on an initial urine screening test for amphetamines. If this happens, another analysis will be conducted for confirmation. Phentermine will not cause a positive result on the confirmation drug test or be reported as positive through the military drug-testing program.

In 2018, the Defense Health Agency (DHA) added four generic weight-loss medications to its pharmacy formulary, including phentermine. The idea is to make more FDA-approved weight-loss therapies available to TRICARE patients but also give active duty personnel struggling with weight some alternatives for meeting standards. The documentation notes that “Active Duty Service Members requiring a weight loss drug should be enrolled in a Service-Specific Health and Wellness Program and must follow individual service policies.”

Will phentermine show up on urinalysis?

If you have taken phentermine, a urinalysis performed to screen for drugs may give a false-positive result for amphetamine. This is because of the chemical similarities between the two drugs.

However, if you can provide evidence that a doctor has prescribed phentermine for you, the result should be declared a false positive.

How can I pass a urine drug test for phentermine?

If you take phentermine, it is advisable to provide your employer with a copy of your prescription before you take the drug test. This proves that you are taking a controlled substance in the manner it was prescribed, avoiding the need for an explanation if the test should return a positive result.

How long does Labcorp take to provide urine results?

Labcorp aims to complete urine testing within a few days, but result delivery times for more complex tests may take longer. However, all tests are usually completed within two weeks.

If you request testing as an individual, your results can be accessed by logging into your Labcorp patient portal account. If your employer requests a drug test, the results will be sent directly to them.

Will Labcorp call you if you fail a drug test?

No, Labcorp will not call you if you fail a drug test. A drug test that detects an illegal substance will either be reported on your patient portal account or sent directly to your employer.

However, Labcorp may call you if they require you to provide a second urine sample, for example, if the first sample was contaminated or invalid for another reason.

How long will phentermine be detectable on a hair drug test?

Phentermine may still be detected in a hair drug test even if you have not taken phentermine for a month or longer. When comparing blood, urine, and hair drug testing, phentermine remains detectable for the longest period of time in the hair.

Does phentermine show up on a 10-panel drug test?

Phentermine may be erroneously categorized as amphetamine as part of the 10-panel drug test, as testing for amphetamine forms part of this particular test. Amphetamine and the other drugs screened for in a 10-panel test are chosen as they are the most commonly misused drugs in the USA.

The panel also includes cannabis, cocaine, barbiturates, opioids, benzodiazepines, phencyclidine (PCP), methaqualone, methadone, and propoxyphene.

Is Adipex a narcotic?

In countries including France, Adipex is considered to be a narcotic. However, in the USA, generic and branded phentermine (such as Adipex) belongs to a group of drugs called sympathomimetics or CNS stimulants.

Is phentermine meth?

No, phentermine is not meth. Phentermine is an isomer of methamphetamine or meth. This means that the two substances are made up of the same atoms, but the atoms are arranged completely differently.

This difference is very important, as it gives the drugs different properties. Despite sharing the same group of atoms, the structure of phentermine makes it far less potent than methamphetamine.

Will Topamax show up on a drug test?

Most drug tests do not test for topiramate or its metabolites. It is, therefore, unlikely that Topamax (the brand name for topiramate) would show up on drug testing.

Sally Cohen

Sally Cohen is a certified nutritionist passionate about promoting health at any size.

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145 Comments

  1. I too am on methadone I started taking Phentermine/adepex aprox 6 plus months ago I dropped 50+ lbs so far, I have random urine tests at the Methadone clinic every month & not one time have I tested positive for my Phentermine/adepex I do have prescription at hand and always am prepared to hand it over if ever needed to but so far I have never had a false positive or not even shown a positive for Phentermine so I’m not sure what the clinic here even tests for but so far they have not accused/asked me for any reasons or proof of prescriptions why a urine test would be positive for drugs not allowed/against the rules without a proper prescription anyways I do believe that Phentermine is not a drug that easily causes false positives on a 10 panel drug screen…I actually had a false positive one time in 3 yrs of a illegal drug that I certainly have not done in 30 yrs & yes it was proven & I was cleared completely & that was before I started the Phentermine I only can think that Benadryl could have made that a false positive… anyways so in my case Phentermine has never even been detected & I do have a prescription if ever need for such an occurrence

  2. Hi! I am currently on methadone as well as phentermine. I have a once a month random urine analysis and for the past 3 months I have tested positive for both methadone and amphetamines on the UA. However this past UA it showed as positive for only methadone. I take my phentermine at the same time everyday and have never missed a dose since beginning the medication. How is this possible? Any input is greatly appreciated! Thanks so much!

    1. Hi Laura,

      The results depend on the type of test. More than that, it’s hard for us to know what might have affected the results, unfortunately.

      You are more than welcome to join our official Facebook support group so you can share your experience with other phentermine users and get feedback on your particular situation: https://www.facebook.com/groups/1069871763087734

      Best regards,

      Sally, Phentermine.com

  3. I began taking Phentermine on Oct 17th. In both Nov & Dec, I tested Positive for Amphetamine. Then, somehow, in Jan I didn’t.
    Yesterday, I was told by my Drs office that I had a Positive drug screen in both Feb & March for METHamphetamine.
    Yesterdays screen was again only positive for Amphetamine.
    Obviously there are some inconsistencies somewhere.
    I am fighting this. I have requested a Hair Follicle test to invalidate those results, as they are most definitely inaccurate.
    My question is; is it even possible for this medicine to show as actual METHamphetamine?

    1. Hi Amanda,

      That shouldn’t happen. However, it really depends on the type of test. As you know, phentermine does have a chemical structure similar to amphetamines, so phentermine weight loss pills can cause a false positive on 5-panel drug screens.

      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.

      In some circumstances, it may be better to inform the lab that you are taking phentermine and 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.

      Sarah, Phentermine.com

    2. Hi Amanda. Im taking methadone and phentermine and have a random monthly urine drug screen. The past 3 months or so I have tested positive for both methadone and amphetamine but this past test a couple weeks ago I only tested positive for methadone. I have not changed anything. I have never missed a dose of my phentermine. How in the world is this possible? The same lab has performed the drug screening with the same methods. I do not understand this. There has been no change to anything. How can it show up one month and not the other???? I am extremely upset about this!

  4. I have taken Mexican Phentermine and I’m afraid it shows on a drug test. What should I do if I don’t have a valid Prescription?

    1. John just stop taken them for a few days I take the Mexican pills aswell they’re called axion but they are phentermine,I go to pain management and I get urine tested so I need to stop taken the pills for a few days I wasn’t aware of phentermine come out false positive for other type of drugs

    1. Hi Steve,

      Most fat burners use natural ingredients that are not restricted and should not affect your testing results.

      Sarah, Phentermine.com

  5. I just took a drug test and phentermine did show as positive for amphetamine. My personal opinion is that it depends on the type of drug test because my Dr office ran a drug test on me and it didn’t show up on theirs.

  6. Last night I had to take a urine drug tests with a split 5 panel. I am taking Adipex for weight loss & have been for about 3 months now. The drug test showed positive for amphetamines. I explained what I was taking, showed them my prescription bottle, & chart information from my doctor. Now I’m just waiting for the call from the MRO at Medtox, which I’ve heard can take up to 7 days. At least I’ll get back pay onde I prove I have a valid prescription for it.

  7. Hi,

    I recently had a drug test for work and took phentermine 7 days prior. I took half a pill for about 3 days then stopped because of the side effects. I was drug tested 7 days later.

    It’s been about 2 weeks now with no call yet. I’ve learned that this is not an acceptable prescription in the industry that I work in so it has me worried.

    I know it’s impossible to to know for sure, but is it likely that it will show up in the test? Thanks.

  8. I took a half of a adipex Tuesday night an I took a drug test Thursday morning I had a 38 hour time line I have never took it before in my life do you thank I should be good ???

    1. Hi Crit,

      It really depends on the type of test. Unfortunately, there’s always a possibility that it could show a false-positive.

      Phentermine should be out of the system in 4 days after the last dose.

      We wish you the best of luck,

      Rebeca, Phentermine.com

    1. Hi Josh,

      There is a possibility that it could show up as a false-positive.Your best bet would be to provide proof of your prescription if this is the case.

      However, it really depends on the type of test and other factors we explained on the article.

      We wish you the best of luck,

      Rebeca, Phentermine.com

      1. I have a drug test that they just inform me about it. My medication is Rx by a doctor. My question is… I have to get the bottle with me as a proof of my Rx to the lab or I will need a confirmation from the pharmacy?

        1. Hi Maria,

          We can’t be 100% sure but showing the bottle with your name on it should provide enough proof of your prescription. Also, depending on the type of test, phentermine might not even show up.

          Hope that helps! You are also more than welcome to join our official Facebook support group: https://www.facebook.com/groups/1069871763087734

          Rebeca, Phentermine.com

  9. I was taking adipex & was getting drug tests that were being sent to the lab. I never once tested positive for it & never tested positive for it for probation neither. Every article I’ve read insisted that it causes false positives for amphetamines & meth but it never did for me.

  10. I took a 37.5 phentermine on a Saturday morning and got a random UA done the following Thursday will that show up as a positive

    1. Hi Natalie,

      Phentermine should be out of the system in 4 days after the last dose.

      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.

      Rebeca, Phentermine.com

        1. Hi Kim,

          Yes, depending on the type of test, it could show a false positive. If this occurs, you can present evidence of your prescription.

          Best of luck,

          Rebeca, Phentermine.com

  11. I last took 30mg of phentermine on Saturday and I have a urine test in 11 days. Will I pass? I have been taking it on and off for over a month.

    1. Hi Patrice,

      Phentermine should be out of the system in 4 days after the last dose.

      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.

      Rebeca, Phentermine.com

  12. Hi Tracy,

    With evidence of your prescription from the doctor who prescribed you phentermine, then the result should be declared as negative.

    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.

    Hope that helps!

    Rebeca, Phentermine.com