Issac Thorne

Last Updated January 9, 2022

How Long Does Phenibut Last?

Like many of you, I've also wondered how long phenibut will last before it wears off.

So, how long does phenibut last? Phenibut will typically last about 2 to 5 hours after kicking in. For most people, phenibut kicks in around the 2-hour mark. Afterwards, the majority of the phenibut “high” has worn off, but you should still some positive after-effects for up to 20 hours or more, depending on your dosage.

However, several variables may affect how long phenibut will last, including:

  • How long it takes phenibut to kick in for you
  • What phenibut dosage you take
  • Your own unique biology
  • The difference between the phenibut “high” and the after effects

Let's take a closer look!

How Long for Phenibut to Kick in?

Having personally used phenibut for over 7 years myself, I find that phenibut takes about 2 hours to really kick in for me.

2 hours in from whatever phenibut dosage I take, I can reliably feel the euphoria and anti-anxiety effects of phenibut working their magic.

Over the years, I've introduced many friends and family members to phenibut. Across the board, most people tend to feel phenibut working at around 2 hours.

Because phenibut's effects can be more subtle than harder drugs, first time phenibut users may claim that they don't feel it yet. This is usually because their expectations are set for a more intense drug experience; by two hours in, the phenibut should absolutely be active in your system.

If you do not feel phenibut working by two hours in, you may notice it with a change ofo environment. Entering a social setting, making a phone call, listening to music, going for a run, etc.

Activities like these will highlight the benefits of phenibut and make it clear that it is in fact working.

You may also benefit from staggering your dosage rather than taking it all at once, which I recommend highly for an optimal experience. More on this in the phenibut dosage guide.

More experienced phenibut users may feel phenibut kicking in earlier. The most likely reason for this is the development of a familiarity for the more subtle benefits of phenibut. After years of taking phenibut, I can feel the subtle come-up about an hour from taking it, or even earlier sometimes.

How Much Phenibut You Take

The amount of phenibut it going to have a massive impact on how long phenibut lasts in your system. This is due to the half-life of phenibut. Every drug has a half-life, which refers to the amount of time that has to go by before the original concentration of the drug is reduced by half.

The half-life of phenibut is about 5.3 hours.

Example: You take 2 grams of phenibut. In 5.3 hours, 1 gram of phenibut remains active in your system.

Taking 2g of phenibut will give you a “phenibut high” for several hours.

Because phenibut usually takes about two hours two kick in, we can say that best effects of phenibut will last from about 2 to 5 hours. Afterwards, the majority of the “high” has worn off, but you should still feel more sociable, euphoric, and positive than usual.

Interestingly, we see that even 20+ hours after taking the 2g phenibut, there is still an active concentration in our body.

For anyone who has taken phenibut on a night out before, this likely comes as no surprise; the following morning you'll often wake up feeling energized, upbeat, and ready to take on the day.

Funny enough, most mornings after a night of phenibut use, I'll feel so good and sociable that I wind up calling all of my friends and family just to talk. This makes phenibut the one supplement I take that also benefits mom!

But How Long Does Phenibut Last in Lower Doses?

How long does phenibut last in lower doses?

2g of phenibut, after 10.6 hours = 500mg phenibut in blood500mg of phenibut, after 10.6 hours = 125mg phenibut in blood

This means that after 10.6 hours, when concentration has been reduced by 75%, the 2g dose will still be felt, while the 500mg dose will be present only in a nearly unnoticable amount.

So, as you can see, the question of “how long does phenibut last,” can be tricky to answer. Phenibut could last almost 24 hours or it could last just a few hours, depending on how much of it you take.

If you're mathematically inclined, this formula can help you figure out how long your intended dose will last you.

Your Own Unique Biology

Half-life and dosage are not the only factors to take into consideration here.

Like any drug, phenibut will affect people differently.

Tolerance, body size/weight, and unique body chemistry are just a few of the factors that play a role in how long phenibut lasts.

My advice is to always start with a small dose, and see how you are personally affected before diving into moderate to large doses.

The Phenibut “High” vs The After-Effects

Finally, it's important to distinguish the difference between the phenibut high and its after-effects.

If you're wondering how long the phenibut “high” lasts, it usually lasts for a few hours after kicking in. In my experience, I would say that it peaks about 2-6 hours after taking taking it. The first two hours are the often unnoticable come-up, and the phenibut high starts wear off after about 6 hours.

The afterglow, of phenibut can often last much longer, however. A higher dose of phenibut (~2g) can last for upwards of 20 hours, maybe more for some people. This accounts for the often pleasant day-after effects of phenibut. It is often described as an “afterglow,” much more pleasant than the hangover that other substances bring.

How Long Does Phenibut Last Before it Expires?

Sidenote: I realize this is unrelated, but some people may have come here hoping to find out how long phenibut “lasts” (as in before it expires).

So, this may vary from vendor to vendor depending on how phenibut is stored and packaged.

Generally speaking, phenibut typically lasts for a few years before expiring.

While I would not recommend consuming any kind of expired supplement, the general consensus tends to be that phenibut maintains a pretty stable shelf life, but may lose potency over time.

Since phenibut is such a cheap and affordable supplement, best to play it safe and dispose of any phenibut that is past its expiration date of a few years.


While there is no easy answer to this question due to so many variables, here are some general takeaways:

  • Phenibut takes about 2 hours to kick in
  • Phenibut peaks from 2-6 hours after consumption
  • When taken in higher doses, the effects of phenibut can be felt for upwards of 20 hours
  • Phenibut is usually good for several years before “expiring”

Please enjoy phenibut and remember to use it safely!


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