There’s no arguing that when you knock back a scoop of pre-workout, you don’t want to be waiting hours for it to kick in.

You’re on your way to the gym, and you’re looking for the blood to course through your veins; the focus and intensity to hit you like a brick wall; and basically, the best performance of your life.

So, having your pre-workout kick in halfway through your lift isn’t going to cut it…

You want focus, drive, intensity, strength, power, and a stellar performance that relies on the ability of your pre-workout to do what it claims.

Whether you’re a rookie to the pre-workout game or a seasoned pro changing up the mix, we’re talking about all things caffeine and how long you’re looking at before you can expect to feel the effects that caffeine has to offer.

Let’s get to it.

Why Caffeine In A Pre-Workout?

When it comes to pre-workout formulas, caffeine is a classic. It’s the gold star of natural central nervous system stimulants that elicits some pretty grand benefits where your workout is concerned. But until that first drop of caffeine hits your bloodstream, you may be a bit groggy and unmotivated walking into your workout.

That’s why we add caffeine to a pre.

While many other compounds—beta-alanine, creatine, nitric oxide enhancers, vitamins and minerals, and the like—are added to support blood flow, nutrient delivery, strength, and power, caffeine works differently.

The intense ability of caffeine to reduce fatigue and improve drive and focus is based solely on its role as an adenosine receptor antagonist.

Here’s how it works.

Adenosine is a compound that naturally occurs in all cells. There are four types of adenosine receptors: A1, A2a, A2B, and A3 that affect the immune, nervous, circulatory, respiratory, and urinary systems 1.

In the brain, adenosine is a key mediator of sleep homeostasis, and extracellular adenosine concentrations rise during wakefulness, especially during prolonged periods of wakefulness, to induce drowsiness and increase sleep pressure (i.e., the desire to sleep).

However, it’s pretty convenient that caffeine and adenosine look structurally similar, which means that caffeine can bind to adenosine receptors in the brain.

By acting as an adenosine receptor antagonist, caffeine prevents adenosine from binding and doing its job, thus drowsiness cannot ensue, you remain awake and alert, and fatigue is delayed. Not to mention that block adenosine also increases stimulatory brain chemicals like dopamine and glutamate.

Thus, through that antagonistic role, caffeine can affect brain functions like sleep, cognition, learning, and memory, and modify brain dysfunctions to potentially prevent the development of chronic cognitive diseases 2.

But there’s another aspect.

Research finds that there may be another aspect to caffeine’s effect on performance, although there isn’t a lot known about them.

Some studies show that caffeine may increase the release of the catecholamine adrenaline (epinephrine), which can help induce secondary metabolic changes that may benefit exercise performance 3, 4.

Here’s a rundown of why moderate doses of caffeine should be part of your pre-workout 5:

  • Increased alertness
  • Better attention
  • Increased concentration
  • Increased focus
  • Increased energy
  • Improved cognition
  • Decreased reaction time
  • Improved productivity
  • Reduced fatigue
  • Improved mood
  • Improvement in team and power-based sports
  • Sustained maximal endurance, resistance and time-trial performance
  • Retardation of exhaustion feeling

In any case, having caffeine in your pre-workout is a staple because of its beneficial role in enhancing cognitive function, sharpening focus, and increasing the intensity of your workout, but how long do you have to wait before you can actually feel those effects?

Caffeine Metabolism

Upon ingestion, caffeine is absorbed via the stomach and small intestine and is evenly distributed through all tissues in the body. Since it’s a lipophilic substance, it easily crosses all tissue membranes, including the blood-brain barrier, to influence cognitive function.

Aside from the dosage, the kinetics of caffeine may be influenced by certain dietary components present in the stomach or GI issues that delay gastric emptying 5, all of which influence how fast caffeine kicks in and how fast it’s cleared from your system.

Studies suggest that plasma concentrations may reach their highest levels after 1-2 hours, with the half-life ranging from 2.5 to 5 hours, although some research suggests it could be upwards of 9 hours depending on the individual. Taken together, there’s significant interindividual variability of absorption and clearance that is affected by 5:

  • Age
  • Sex
  • Hormones
  • Training level
  • Body composition
  • Genetics
  • Underlying diseases
  • Smoking
  • Diet and alcohol

How Long Does It Take Caffeine To Kick In?

The rate at which caffeine kicks in for you isn’t going to be the same as it is for your gym buddy. Individual differences in body biochemistry are largely responsible for the rate at which your body metabolizes caffeine.

Generally speaking, the effects are felt quite rapidly, but when it comes to when those effects stop, it’s going to be different. For some people, it’s quite fast; for others, it’s pretty slow.

It’s also the same reason some people can have a cup of coffee before bed and sleep like an angel, while others are left twiddling their thumbs until 4 am.

As a general rule, the effects of caffeine can be felt anywhere from 15 to 90 minutes after consumption, with plasma concentrations reaching their peak around 30 to 90 minutes after ingestion regardless of the dosage 6.

Studies suggest that in humans, 99% of caffeine is absorbed within 45 minutes of ingestion, with roughly 20% being absorbed from the stomach and the remainder in the small intestines 5. For a healthy adult male, absorption of 5 mg/kg caffeine would reach peak plasma caffeine concentration in about 30 minutes.

However, depending on the formula you’re taking, that may be extended, as those times indicate pure caffeine anhydrous.

While there’s no perfect time to take your pre-workout, researchers speculate that the “ideal” ingestion time for any sort of caffeine supplementation isn’t related to the time it peaks in the bloodstream but rather the greater “window” of possibility dictated by caffeine metabolism—approximately 1-3 hours 7.

A Word Of Caution

If you look at any pre-workout label, you’ll see a wide variation in caffeine dosage. Some offer just 50mg for sustained and clean alertness, while others offer upwards of 300mg in a single scoop giving you a powerful punch of CNS stimulation.

And while it may seem like a good idea at the time to shoot back a few hundred milligrams of caffeine in a single go to get the most out of your workout, knowing how caffeine affects you is key to avoiding the nasty side effects that go along with high-stim products like jitters, nervousness, anxiety, and general symptoms of overstimulation. They can hurt your performance more than they can help it.

But what’s interesting is that where caffeine is concerned, more is not better. Studies actually find that consumption of lower doses of caffeine (3mg/kg bodyweight) resulted in greater effects on cognition and brain activation compared to moderate and higher doses (6 or 9 mg/kg bodyweight) 6.

Research finds that lower doses may be enough to induce saturation of the effect of caffeine on the central nervous system.

Final Thoughts

Knocking back a scoop of pre-workout can sometimes be like playing Russian roulette. Will it hit me on the drive to the gym, or will it hit me when I’m almost done with my workout?

The truth is that there’s no guaranteed time that caffeine will kick in and ramp up your alertness, so it’s about testing and seeing how your pre works.

For most—Pre Lab Pro® included—knocking it back 30 minutes before your workout should safeguard you against having it hit before you start your workout, but also ensure it’s not going to hit after it’s already done.


  1. S Singh, R McKintosh. Adenosine. [Updated 2021 Jul 13]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Available from:
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  3. DL Costill, GP Dalsky, WJ Fink. Effects of caffeine ingestion on metabolism and exercise performance. Med Sci Sports. 1978;10(3):155-158.
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  7. DG Bell, TM Exercise endurance 1, 3, and 6 h after caffeine ingestion in caffeine users and nonusers. J Appl Physiol (1985). 2002;93(4):1227-1234.