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7 ways caffeine pills can benefit your mental and physical performance

Written by John Davis

Last updated: March 29, 2023

Caffeine pills are the most effective way to get a precisely-calibrated dosage of caffeine. For both physical and cognitive performance, caffeine’s use as a performance enhancer is almost without match.

Caffeine boosts strength, speed, cognition, and alertness across a wide range of tasks and settings, while having a great safety profile in its effective dosage range.

Looking to optimize your caffeine usage? Here’s what our research team found out about the biggest benefits of caffeine pills, whether your goal is superior physical performance, enhanced cognitive performance, or improved alertness.

Caffeine pill benefits

1. Caffeine is one of the oldest and most versatile supplements in use

Taking caffeine pills can be helpful whether your goal is to run faster, lift more weight, study harder, or be more vigilant.

Caffeine’s effects across a wide variety of tasks are well-characterized, so it’s very easy to figure out how much caffeine you’ll need and when to take it in order to meet your performance goals.

2. Caffeine can improve lifting performance

For resistance training, as well as other high intensity, short duration exercise, caffeine appears to blunt feelings of fatigue, increasing your ability to lift more weight for more reps, which is why caffeine is a popular ingredient in pre-workout shakes.

One study, published in 2007 in the International Journal of Sports Physiology and Performance studied the effects of a dose of caffeine on bench press and leg press in a group of volunteers (1).

 The researchers found that bench press maximum reps (at a constant weight) increased from an average of 10 in the control group to an average of 12.5 in the group given caffeine.

The subjects given caffeine reported feeling the same level of fatigue as the subjects given the placebo, indicating that the caffeine increases your performance across the board. In other words, applying the same effort results in better performance after you’ve taken caffeine.

3. Caffeine improves endurance

A systematic review published in 2009 in the Journal of Strength and Conditioning Research looked at 21 different studies of caffeine’s effect on endurance performance (2).

After reviewing the data and pooling results, the researchers concluded that caffeine can improve endurance performance by three percent or more.

That may not sound like much, but it would amount to finishing a marathon about a mile ahead of where you’d be without caffeine. Moreover, these findings were robust and supported by many studies.

4. Caffeine is also well-suited for boosting anaerobic exercise performance

That was the conclusion of a 2009 publication in the journal Sports Medicine (3). Caffeine is especially useful if your bout of exercise is going to last at least 60 seconds in duration. 

5. Caffeine can boost reaction time, mood, and alertness

The benefits of caffeine extend to mental tasks, too. A scientific article by R. H. S. Ruxton found that moderate caffeine consumption improves reaction time, boosts mood, and increases alertness (4).

Perhaps most importantly for mental performance, it also increases your short term memory recall: this means you can keep more pieces of information in your head at once, making your studying, planning, and work on cognitively demanding tasks much more effective.

6. L-theanine enhances the mental benefits of caffeine

There is a large body of evidence that these two compounds work together to boost your mood and mental function beyond what caffeine normally can do.

Initial evidence for this effect came from studies of the mood and mental acuity boosting powers of green tea extract; researchers noted that L-theanine appeared to account for some of the effects independent of caffeine (5).

Direct studies of the combined effect of L-theanine and caffeine started to explore the effects of both together. A paper published in 2008 in the journal Psychopharmacology examined just this combination (6). The researchers found that, while caffeine alone has a tendency to cause jitteriness, when combined with theanine, this tendency disappears.

This is good news for people who are sensitive to the negative effects of caffeine, because it suggests they can be blunted or prevented by a caffeine pill which also includes theanine.

7. Caffeine pills are an effective way to increase caloric expenditure

One consistent finding from epidemiology research is that people who drink coffee and tea are less likely to be overweight.

This association remains, even after controlling for other factors like dietary patterns. While additional phytonutrients definitely play a role in this relationship (hence green tea extract and green coffee bean supplements), there’s no denying the role of caffeine in these relationships.

Research published as early as 1990 demonstrated that caffeine exerts a significant thermogenic effect: a study in the Journal of Clinical Nutrition used healthy volunteers who took increasing doses of caffeine, and was able to show that the thermogenic effects of caffeine increase linearly as a function of the dosage (7).

Moreover, the researchers found that caffeine alters specific biochemical pathways, leading to changes in cellular metabolism. Other work published in the American Journal of Clinical Nutrition showed that this thermogenic effect works in lean people as well as formerly obese people who have finished a weight loss program (8).

Caffeine pill side effects

Caffeine can cause adverse effects when taken at high doses. Given that it is so potent, it should not be surprising that caffeine has some side effect when taken in excess. According to the Mayo Clinic, taking too much caffeine (defined as over about 400 mg per day) can lead to headaches, nausea, insomnia, restlessness, tremors, and a rapid heartbeat (9). Extremely high doses have even been associated with fatal overdoses.

Make sure to monitor your overall caffeine intake, not just from dedicated caffeine pills. When taking caffeine pills, it’s important to know where the other sources of caffeine in your diet are.

If you already are taking a weight loss supplement, for example, you might be getting a substantial dose of caffeine as it is. Caffeine’s effects take several hours to wear off, so spread out the caffeine you do consume throughout the day.

Caffeine pill dosage

Scale caffeine dosage to your body weight. Caffeine is most effective when its dosage is calibrated to your body weight. Most scientific studies recommend doses of three to six milligrams of caffeine per kilogram of body mass.

This means that if you weigh 80 kg (175 pounds), you will see optimal results at doses of caffeine between 240 to 480 mg of caffeine. Sometimes it’s hard to get exactly the correct dosage, given that caffeine pills usually come in multiples of 100 mg, but the dosage of caffeine is fairly forgiving.

Doses as low as 3 mg per kg are effective at generating most of caffeine’s benefits. Some research suggests that doses that are pretty low (below 3 mg per kg) are still effective (10). As far as timing, you’ll want time your caffeine intake so that you take a caffeine pill about 60 to 90 minutes before when you want to be at peak performance.

The effects last for several hours, so you don’t need this timing to be perfect. A time release formulation will help deliver a longer, steady stream of caffeine to keep you operating on a high level for a long time, but this might happen to the detriment of absolute peak performance. 

This is a worthy trade, though, if you need to be working at high intensity (mentally or physically) for several hours at a time.

Caffeine pill benefits FAQ

Q: What do caffeine pills do to your body?

A: Caffeine is a potent stimulant that modulates your body’s central nervous system, which accounts for its broad-reaching physical and mental effects.

Boosting athletic performance and cognitive performance at the same time is very hard to do unless you act on the central nervous system, which is exactly what caffeine pills do.

Additionally, caffeine also ramps up your body’s cellular metabolism, which boosts your baseline energy expenditure (and accounts for the thermogenic, weight-loss friendly effects of caffeine pills).

Q: When should you take caffeine pills?

A: The optimal timing for taking a caffeine pill is about an hour or so before you need to perform at your best. You should also keep in mind the “come-down” from caffeine; given that caffeine (obviously) inhibits your ability to sleep, you should also time your caffeine pill dose so that it doesn’t keep you up super late, unless that’s what you want.

You’ll get maximum performance benefits from caffeine for a few hours, so you have some flexibility with when you take caffeine pills.

For weight loss, in contrast, you want to maintain a moderate level of caffeine throughout the day, so it’s best to take a caffeine pill early in the day, then let the long elimination half life of caffeine sustain your body’s caffeine levels throughout the day.

Even ten to twelve hours after taking 200 mg of caffeine, you’ll still have an effective dose of 50 mg in your body.

Q: Are caffeine pills bad?

A: Caffeine pills get a bad rap because it’s quite easy to overdo it: the relatively long delay (60-90 minutes) between taking a pill and experiencing its full effect, and the high dosage per pill that’s common in many over the counter caffeine pills, makes it easy to blow past the optimal dose and get jitters and anxiety.

Caffeine does have some serious negative side effects if you take it in extremely large doses, but when taken at moderate doses it’s both well-tolerated and remarkably effective.

Many of the physical, cognitive, and fat-burning effects that people strive to get through complicated combinations of herbal compounds could be much more easily garnered with a 150 or 200 mg dose of caffeine.

So, caffeine pills are only bad if you don’t use them intelligently. At the right dose, caffeine is a very effective and versatile supplement.

Q: How long does a caffeine pill last?

A: You can expect the greatest effects of caffeine to last for a few hours. It takes an hour or so for a caffeine pill to achieve maximum effect, and by five or six hours, the effective dosage has dropped in half (this time duration is called the elimination half life).

One important thing to note about the effects of caffeine, and its elimination half life, is that it can be much longer (sometimes doubling the half life to ten or twelve hours) in women who are taking birth control pills, due to an obscure interaction.

This doesn’t have any real consequences in terms of caffeine’s efficacy; it just means that caffeine will last a lot longer in your system in this case, so you’ll have to be more thoughtful about when, if at all, to take another caffeine pill.

Q: How are caffeine pills made?

A: Caffeine pills are usually made by purifying the caffeine that’s extracted from decaf coffee during the decaffeination process.

A solvent, usually water or supercritical carbon dioxide, is used to pull the caffeine out of the coffee beans. The beans then become decaf coffee, and of course the caffeine is left over and can be purified and packaged into caffeine pills.

It’s also possible to synthesize caffeine, but given the amount of decaf coffee that’s made every year, coffee beans are a more common source.

The pure caffeine powder is then pressed into tablets or pushed into capsules, along with binders and stabilizers (hopefully not too many).

Related: Our best caffeine pill picks


Caffeine is one of the oldest and most reliable performance-enhancing supplements out there. Whether you need extra power and endurance for a workout, a jolt of energy for a late-night work session, or increased vigilance for difficult cognitive tasks, caffeine pills are a rock-solid reliable way to get the most out of caffeine’s numerous benefits.

Many of caffeine’s benefits don’t require super high doses, either, so you can get the benefits without the jitters, nervousness, and other side effects that can be triggered by excessive caffeine intake. Some of these side effects can also be combated by taking a caffeine pill that also delivers L-theanine.


John Davis

John Davis is a Minneapolis-based health and fitness writer with over 7 years of experience researching the science of high performance athletics, long-term health, nutrition, and wellness. As a trained scientist, he digs deep into the medical, nutritional, and epidemiological literature to uncover the keys to healthy living through better nutrition.