How long does Adipex stay in your urine? (3+ factors to be considered)

This article will discuss the approximate stay time of Adipex in urine. We will also discuss some factors that may affect this time duration in some individuals and how one can ensure the safe and effective use of Adipex.

How long does Adipex stay in your urine?

Adipex (Phentermine) can stay in your urine for about 48-92 hours (2-4 days) (1). The terminal half-life of this medication is 20 hours, but the process of elimination can be carried out more rapidly if the urine is acidic (1).

This is because acidic urine can enhance the degradation of the drug and its subsequent removal from the body. It can also make it more soluble in urine.

Since Adipex is 80% removed via urine in an unchanged form, the drug’s half-life reduces from 20 hours to 7-8 hours in case of acidic urine (pH less than 5). (1)

However, it’s important to note that the exact time duration can vary from person to person, as different factors could affect it – like metabolism, dosage strength, and individual differences.

Factors affecting the stay time of Adipex in your urine

The following factors can affect the stay time of Adipex in your urine (1):

  • Metabolism – How fast your body processes the drug can impact how long it stays in your system.
  • Dosage – Higher Adipex doses can take longer to eliminate.
  • Frequency – the more frequently you use Adipex, the longer it stays in your urine. 
  • Hydration – Drinking plenty of water can help flush the drug out of your body. Frequent urination can rapidly remove the drug.
  • Liver and kidney functions – These are the primary organs responsible for drug elimination. If these organs don’t work properly, the drug could stay longer in your system overall.
  • Use of other medications – Some medications can interact with Adipex, either prolonging or shortening its presence in your system.

These factors can vary from person to person, as each individual is unique and can have different factors affecting their health. 

How to address Adipex showing up on a drug test concern?

If you’re concerned about Adipex showing up on a drug test or making you fail one, please talk to your healthcare provider.

Adipex does not generally show up on a drug test, but in some cases, it has caused a false positive for Amphetamines and has shown up as Adderall (2). This can cause a person to be concerned about going for a drug test while taking this medication.

The best way to deal with this situation is to inform the drug testing authority about all the medications you’re currently taking before the test. You can also submit your prescription as proof to the authority.

False positives are common and even OTC medications can cause them. This is why there is nothing to worry about as long as you’re just following your doctor’s directions and taking prescription medications.

How to ensure the safe and effective use of Adipex?

The following points are important to ensure the safe and effective use of Adipex (3):

  • Take Adipex exactly as prescribed by your healthcare provider.
  • Drink plenty of water while taking the medication.
  • Make sure you follow a good diet and exercise regimen to enhance the effects of Adipex.
  • Keep an eye out for any side effects and report them to your doctor.
  • Avoid the use of alcohol with Adipex.
  • Take Adipex early in the day to prevent insomnia at night.
  • Keep a record of your weight loss journey to monitor the effectiveness of Adipex. 


In this article, we have discussed the approximate stay time of Adipex in urine. We have also discussed some factors that can affect the time duration and what you should do if you’re concerned about getting a false positive on a drug test. 

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PubChem [Internet]. Bethesda (MD): National Library of Medicine (US), National Center for Biotechnology Information; 2004-. PubChem Compound Summary for CID 4771, Phentermine; [cited 2023 Aug. 21]. Available from:


Alyson Schwebach, Jennifer Ball. Urine Drug Screening: Minimizing False Positives and False Negatives to Optimize Patient Care. US Pharm. 2013;38(12):1-6. Available at:


LABEL: ADIPEX-P- phentermine hydrochloride tablet. ADIPEX-P- phentermine hydrochloride capsule. DailyMed [Internet]. Available from: