How Long Does Phenibut Stay in Your System?

Written by Melissa Carmona

& Medically Reviewed by Dr. Kevin Wandler, MD

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Last Updated - 07/21/2022

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Updated 07/21/2022

Phenibut is a substance often described as a nootropic, which some people say are substances with cognitive benefits. In the United States, Phenibut is sold as an unregulated substance or supplement, although in countries like Russia, it has a long history as a prescription anti-anxiety medication.

The structure of Phenibut is similar to gamma-aminobutyric acid or GABA. As a result, it can have a calming effect and may reduce anxiety. Additionally, some people may use phenibut for fear, insomnia, stress, fatigue and post-traumatic stress disorder. At lower doses, phenibut may increase sociability and cause euphoria when used recreationally. Higher doses of phenibut may lead to coordination and balance impairment. So, how long does phenibut stay in your system? While it can take up to 30 hours for phenibut to leave the body, its impacts and traces can remain longer.

How Is Phenibut Used?

Phenibut is most often taken orally, and is available in pills, capsules, or a powder that’s placed on the tongue. All of these products are available online in the U.S.

How Long Does a Phenibut High Last?

How long does phenibut last? It depends. One of the biggest factors that play a role in how long a phenibut high lasts is the dosage used. A single dosage of phenibut is usually around 750 to 1500 mg.

What’s important to note is that since phenibut is unregulated, there are no guidelines as to how much is safe versus what might constitute an unsafe dosage. This is one of the biggest problems with supplements that are sold without regulation.

When someone uses phenibut it can take thirty minutes or more before the effects are felt. A dosage of phenibut will last for most people around six hours, although there may be some lingering effects for around six hours.

Phenibut Half-Life

Half-life is a measure of how long it takes a substance to be reduced by half in the body. With most substances, it takes several half-lives for the substance to leave the system fully. The phenibut half-life is around 5.3 hours.

How Long Does Phenibut Stay in the Body?

Based on the average half-life of phenibut, which is 5.3 hours, it can take up to 30 hours, on average for phenibut to leave the body. Factors that can play a role in how long phenibut stays in the body are:

  • Dosage
  • How often someone uses phenibut
  • Age (it tends to take longer for substances to leave the body of older people than younger people)
  • Metabolism
  • Overall health
  • Hydration level

If someone regularly uses phenibut, it can take longer than 30 hours for it to leave their system because it can build up in the body

How Long Does Phenibut Stay in the Urine?

Some people question how long phenibut stays in urine. Phenibut doesn’t show up on drug screenings. While it has psychoactive effects and is potentially addictive, it’s not currently a controlled substance in the United States. If someone was specifically being tested for the use of phenibut, which would be unlikely, it could show up for anywhere from four days to four weeks in a urine test. In a blood test, phenibut may show up for up to 80 hours after the last dose.

While most screenings including a standard 5-panel screening won’t test for phenibut, there is a rare chance that the use of phenibut could show up as a false positive for benzodiazepines. Even so, not all screenings even look for benzodiazepine use.

Help for Phenibut Dependence & Addiction

If you struggle with phenibut addiction or dependence, contact The Recovery Village at Palmer Lake to learn about our substance abuse treatment programs and options. We have a proven track record of providing caring and successful substance abuse treatment at our Palmer Lake, Colorado facility. We also offer free resources, such as online recovery meetings, free chat rooms, and much more.


Ahuja, Tania; Mgbako, Ofole; Katzman, Caroline; Grossman, Allison. “Phenibut (β-Phenyl-γ-aminobutyric Acid[…] Nootropics of Abuse.” National Center of Biotechnology Information. April 30, 2018. Accessed, April 13, 2019.


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