Phenibut Side Effects – Is Phenibut Safe?

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Phenibut is a powerful anxiolytic drug popular within the nootropic community. When taken in low doses, user reviews and limited studies suggest that this drug helps to encourage a positive and calm mood while enhancing cognition.

It is used as a prescription drug in Russia for the treatment of anxiety, depression, difficulties sleeping, PTSD, and asthenia. (1,2) There are no published human trials available outside of Russia, which makes drawing conclusions about the safety and side effect profiles of Phenibut challenging. Animal studies support the use of Phenibut for anxiety, fear, aggression, memory, learning, and neuroprotection. (3,4,5,6,7,8)

Understanding not just the benefits, but also the risks and potential negative side effects, of any nootropic supplement that you add to your stack is of critical importance.

This understanding can help you to determine your dosage, how often you take the drug, and what other drugs you stack it with. It can help you to pinpoint when you are experiencing side effects so that you can adjust your dosage or eliminate a nootropic altogether.

Intermittent and low doses of Phenibut are generally well tolerated. When taken in higher doses, or daily for extended periods of time, Phenibut is know to come with a side effect profile that users need to be aware of.

Common Side Effects

Largely thanks to user reviews and animal studies delving into the mechanisms of action of this compound, a fairly good understanding of the risks of supplementation can be drawn.

Side effects reported by user reviews at lower doses include:

  • Headache
  • Loss of appetite
  • Dizziness
  • Nausea
  • Anxiety
  • Mental and physical fatigue
  • Sleepiness
  • Mild stimulation

When taking higher doses, many users report feelings similar to being drunk or sedative effects, similar to those of powerful anxiolytic prescription drugs like Xanax. In addition to the side effects listed above, at high doses users have reported:

  • Heart palpitations
  • Respiratory depression*
  • Motor Impairment and trouble with balance
  • A “hangover” like effect

Heart Palpitations

One user on Longecity reported waking up and feeling terrible, as if he'd drank too much alcohol and felt his ears ringing. He then experienced severe heart palpitations, describing it as "thudding extremely hard in my chest." He said he felt like it stopped at one point before rapidly resuming rhythm again.

Another user, who claims he "read up on it" before taking a large dosage, reported "dreadful side effects" once he discontinued usage. He says he had a strong heart, but regardless, his experience landed him in the hospital with several heart palpitations, anxiety, and cold sweats.

Other users report feeling like their heart rate is jacked up like they just finished a set of sprints. Irregular heart beat was commonly reported, varying from fast to slow.

Respiratory Depression

*Respiratory depression and some other more serious side effects are most common when mixing Phenibut with other depressant drugs, including alcohol, Xanax, opioids, and tranquilizers.

Loss of Appetite

One user reported feeling a varying effect in appetite, depending on the kind he was consuming. He said the "large crystals would completely destroy appetite" and he wouldn't feel like eating for several days.

Deep Depression

One Longecity user reported feeling like he couldn't use the muscles in his face to form a smile. He said the depression was very deep, and he didn't even feel like responding to texts or calls. He would spend his day on his couch staring at the TV like a zombie, not feeling awake or asleep hours.

Overdose Side Effects

You can overdose with Phenibut. An overdose can lead to lowered blood pressure, liver or kidney problems, and seizures, among other serious adverse reactions. An overdose is far more dangerous when combined with other depressants, including alcohol, opioids, narcotic drugs, or sedatives.

Phenibut Long-Term: Withdrawal

Thanks to how Phenibut works, people can rapidly form a tolerance. This tolerance leads to lack of efficacy at standard doses, and even withdrawal symptoms after cessation.

You can tell that you are developing tolerance when the same dosage that has worked for you in the past does not yield the same results. The last thing you want to do in this situation is increase your dosage when it stops working - high doses increase side effect risk and likelihood of difficult withdrawal symptoms. If too much Phenibut is taken for too long of a period of time, this may lead to health complications, particularly liver health.

Phenibut withdrawal can lead to feelings of:

  • Anxiety
  • Depression
  • Insomnia
  • Restlessness
  • Agitation
  • Reduced appetite
  • Brain fog that can last for days or weeks
  • General fatigue
  • Trouble thinking clearly
  • Heart palpitations

There is one case study examining a 35 year old male in the US with Phenibut dependence. (2) Initially the drug helped him with insomnia, alcohol cravings, and anxiety. By the time he checked himself into a clinic, he was experiencing withdrawal symptoms so severe that they would kick in 3-4 hours after supplementation, and resulted in his inability to work or get along with his family. He was taking very high daily doses of both Phenibut (8 g/day) and kratom (18 g/day).

It took 9 weeks of gradually substituting Phenibut with Baclofen, and 12 additional weeks to then taper off of Baclofen, before he could fully resume his normal life.

The good news? His story is not typical, and if you arm yourself with the appropriate knowledge, you can avoid dependence and withdrawal. There are many strategies that will help keep you safe from the more severe side effects attributed to this supplement. If you use Phenibut cautiously, you can experience the benefits without a high risk of adverse side effects.

How to Avoid Phenibut Side Effects

It is important to recognize that a safe dose for one person may be too much for another person - everyone’s response to this nootropic will differ. Due to the risk of side effects and withdrawal, it is recommended to start out with very low doses of Phenibut and slowly work up until the ideal dosage is found.

Most users take between 250 and 1,000 mg/day, either in one dose in the morning or split between one dose in the morning and the second around lunchtime. This compound is not completely eliminated from your body until around 24 hours post ingestion, so it is important not to re-up on the same day, but rather slowly increase your dose until you find your sweet spot.

While some people do report needing more than 1,000 mg/day, it is important not to exceed 2,000 mg/day to protect your health.

Another good idea is to either cycle with Phenibut or only take it intermittently, on days where you really need an extra anxiety-fighting boost. Limiting your use to only a couple of times per week may be best.

A common cycling schedule can be two days on, two days off, or one week on, one week off. User reviews vary on how long it takes to feel tolerance, with some reporting up to one month being alright, but other users stressing never to take it daily for more than one week in a row.

Final Thoughts

Phenibut can be a safe nootropic for stress, mood, and overall cognitive function if taken cautiously. However, if large doses are taken, you take it daily, or you mix it with other depressant drugs, dangerous side effects can occur.

If you would like to learn more about Phenibut, check out our additional articles on user reviews, where to buy, and Phenibut overview.


About Nicole Gleichman

Nicole Gleichmann is an avid self-improvement enthusiast who loves to help her readers become the best versions of themselves. For the past five years, she's dedicated her life as a wellness writer and nutrition coach to learning everything there is to know about human potential. In her free time, she spends her days traversing the mountains, playing with her dogs, and traveling the world in search of new perspectives. Nicole's journey towards discovering the body's potential started with her undergraduate degree in Organismal Biology. Since that time, she's worked with fitness experts, naturopathic doctors, and other health and wellness professionals, learning all she can along the way. Nicole's experience is in an Organismal Biology degree, 5 years in health and wellness writing and research, and 3 years as a nutrition coach.