Will Phentermine Show Up On A Drug Test?
In our latest question and answer, the pharmacist discusses whether or not phentermine will show up on a drug test.
I just took a Phentermine at 11:04 am Sunday. I have to take a drug test by 4:30 pm this Tuesday (2 days away). I have a high metabolism and I drink lots of water. Can I pass this test by then? I've only taken one and won't take another
Sep 02, 2022- Phentermine is not on standard drug screens but can cause false positives for amphetamine and methamphetamine, so inform your doctor and the testing facility of all medications you take.
- Phentermine can remain in your system for nearly 5 days, so it may still show up on a drug test within 2 days of taking it.
- Most drug testing facilities will clear a positive result if you provide a valid prescription for phentermine.
Answer
Phentermine can be detected on urine drug tests if it is being tested for. However, it is generally not part of your standard 5 or 7-panel drug screen.
However, and this is an important point, phentermine is closely related to amphetamine, and has been reported to cause false-positive tests for both amphetamine and methamphetamine. Therefore, it is important to let your doctor and tester know all the drugs you are taking to avoid any confusion with the results.
How Long Does Phentermine Last In Your System?
Based on the pharmacokinetic profile of phentermine, it can last in your body for nearly 5 days as the half-life of the drug is relatively long, around 19-24 hours.
In terms of drug testing specifically, most institutes allow you to give them a list of prescription medications when a drug screen comes back positive, so when you are able to provide a prescription for phentermine they likely will report back to whoever ordered the drug screen that you are clean.
Phentermine Information
Phentermine is a stimulant that suppresses appetite and is used to treat obesity. This is a controlled substance, so it can only be obtained by a prescription in the United States. This medication is typically dosed 1-2 times a day and this is due to the fact that this medication has a long duration of action in the body (around 8-14 hours) and a single dose can stay in the body for upwards of 100 hours.
Phentermine Drug Testing
On most five-panel drug screening tests, they will test for amphetamines. When a patient does test positive for a substance, most drug screening facilities will allow the patient to provide prescription medication lists as there are a number of prescription medications (phentermine included) that will cause a false positive.
When a prescription for a medication is provided they typically amend the drug test to show that there is, in fact, no positive result when reporting to the party who ordered the test.
Based on the time frame you provided (2 days), it will most likely take longer than that for phentermine to leave your system and you likely will have a positive drug screen for some form of amphetamine (e.g. methamphetamine). It may be a good idea to determine up front how to provide the drug screening institution with a list of your prescription medications so that they are better able to evaluate your drug test.
Final Words
Thanks for your question and feel free to reach back out in the future!
References & sources
- Phentermine Prescribing Information — PubMed
- SAMHSA Guidelines for Drugs of Abuse Testing — Thermo-Fisher
Glossary — Terms in This Answer
- Half-life
- The amount of time it takes for half of a drug's concentration in your body to be eliminated.
- Pharmacokinetic profile
- The way a drug moves through and is processed by the body over time.
- Stimulant
- A medication that increases activity in the brain and nervous system, boosting alertness and energy.
- Controlled substance
- A drug regulated by the government that can only be legally obtained with a doctor's prescription.
- Duration of action
- The length of time a medication remains active and effective in the body.
- False-positive
- An incorrect test result showing the presence of a substance when it is not actually present.
- Five-panel drug screening
- A urine test that checks for five common categories of drugs: amphetamines, cocaine, marijuana, opioids, and PCP.
- Amphetamines
- A class of stimulant drugs that increase alertness and energy, including prescription medications and illegal drugs.
Dr. Brian Staiger, PharmD
Doctor of Pharmacy, board certified clinical pharmacist (BCPS), American Herbalist Guild, Medication Therapy Management certified
Brian Staiger, PharmD, BCPS, is a licensed pharmacist with more than 13 years of experience across retail pharmacy, clinical pharmacy, medication safety, pharmacy program development, and healthcare administration. He is the founder of HelloPharmacist.com, where he helps patients...
More answers from Brian →