Caffeine pre-workout — the minimum effective dose is 2 mg/kg, not 6
Caffeine pre-workout: dosage and evidence in the table. u Bucha.
Most pre-workouts claim to have an "advanced energy formula" with caffeine, often not specifying the exact dose or providing a dose that is too high for minimal needs. Meanwhile, the International Society of Sports Nutrition in its consensus statement from 2021 indicates that the ergogenic effect of caffeine is significant already at 2 mg/kg of body weight — not 6 mg/kg, as aggressive marketing messages suggest (Guest et al., Journal of the International Society of Sports Nutrition, 2021). This article breaks down the topic into its components: how much, when, and for whom.
KEY INFORMATION
• The minimum effective ergogenic dose of caffeine is 2 mg/kg of body weight (ISSN, 2021).
• A range of 3–6 mg/kg provides submaximal to maximal effects; above 6 mg/kg there are no benefits with increased risk of side effects.
• Caffeine works by blocking adenosine receptors A1 and A2A, which delays the feeling of fatigue.
• The pre-workout effect is effective in both endurance and strength sports.
• Regular caffeine consumption builds tolerance — a 3–7 day break restores receptor sensitivity.
How does caffeine affect the body during training?
Caffeine blocks adenosine receptors A1 and A2A in the brain and muscles — adenosine is a neurotransmitter that accumulates during exertion and signals fatigue. By blocking its receptors, caffeine delays the feeling of exhaustion, which translates into the ability to train longer or more intensely (ISSN, 2021). This effect is well documented in hundreds of randomized clinical studies.
In addition to blocking adenosine, caffeine stimulates the release of catecholamines (adrenaline and noradrenaline), which mobilizes energy resources: it releases fatty acids from fat tissue and glycogen from the liver. Therefore, caffeine can improve both aerobic performance (more energy from fats) and anaerobic performance (greater muscle contraction strength). This wide range of action distinguishes caffeine from most other ergogenic substances.
Is the effect of caffeine "real" or just psychological? This question often arises. Studies with blinded groups exclude the placebo effect: caffeine works regardless of whether the subject knows they have taken it. A meta-analysis of 300 studies published in British Journal of Sports Medicine confirmed an average performance improvement of 2–16% across various sports disciplines when using caffeine vs placebo (Grgic et al., BJSM, 2018).
Caffeine Dosage Table for Pre-Workout
The table below is based on the ISSN recommendations from 2021 and systematic reviews from Cochrane and BJSM. Doses are given per kilogram of body weight — this is the only precise method for dosing ergogenic substances, as the physiological response depends on mass, not on "one capsule for all".
| Dose (mg/kg) | Weight 60 kg | Weight 75 kg | Weight 90 kg | Expected effect | Notes |
|---|---|---|---|---|---|
| 2 mg/kg | 120 mg | 150 mg | 180 mg | Minimum effective — reduction of fatigue, improvement of focus | Good for those sensitive to caffeine and beginners |
| 3 mg/kg | 180 mg | 225 mg | 270 mg | Optimal ergogenic effect | Recommended by ISSN as a starting point |
| 5 mg/kg | 300 mg | 375 mg | 450 mg | Maximum effect — significant improvement in endurance and strength | Requires established tolerance; caution regarding sleep |
| 6 mg/kg | 360 mg | 450 mg | 540 mg | Threshold with no additional benefits | Increased risk: tachycardia, tremors, sleep disturbances |
| >6 mg/kg | >360 mg | >450 mg | >540 mg | No additional benefits; risk of caffeine poisoning | Not recommended; possible ergolytic effect |
| When to take it? 45–60 minutes before training. Brewed coffee: 60–90 minutes before (slower absorption). EFSA: the safe daily dose for adults is ≤400 mg from all sources. | |||||
Why is 2 mg/kg the minimum, not zero? Doses below 2 mg/kg are too low to exceed the threshold for blocking adenosine receptors sufficient for measurable performance improvement. They do, however, affect focus and mood — these are different mechanisms than purely physical effects. If the goal is a specific improvement in sports performance, 2 mg/kg is the absolute minimum to start with.
Does caffeine improve strength before strength training?
A meta-analysis of 21 randomized studies published in Journal of Strength and Conditioning Research showed that caffeine at doses of 3–6 mg/kg increases maximum strength (1RM) on average by 3–4% and the number of repetitions to failure by 5–8% (Grgic et al., 2018). This may sound modest, but in the context of sports, a 3–4% difference in maximum strength translates into real gains.
Interestingly, the effect of caffeine varies depending on the muscle group. Studies consistently indicate that strength improvement is more pronounced for the upper body (bench press, rowing) than for the lower body (squats, legs). The mechanism is not fully understood — differences in the density of adenosine receptors in fast-twitch muscles are suggested.
We have noticed that users of pre-workout supplements often do not distinguish the effect of caffeine from the effects of other ingredients in the formula (beta-alanine, citrulline, creatine). Caffeine acts here as an "amplifier of focus and endurance", not as a buffer for lactic acids (that’s beta-alanine) or a "pump" for blood vessels (citrulline). Precise dosing of caffeine alone provides a clearer picture of its actual effect than using mixed formulas.
For mixed sports (HIIT, crossfit, combat sports), caffeine at 3 mg/kg improves both aerobic endurance and reactive speed. A Cochrane review from 2020 confirmed that caffeine is one of the best-researched ergogenic substances available to athletes over the counter, with measurable performance improvements across a wide range of disciplines (Cochrane, 2020).
Caffeine timing — when exactly to take the dose?
The pharmacokinetics of caffeine are well described. After oral intake, caffeine is absorbed from the intestines and reaches peak blood concentration after 45–60 minutes (some sources state 30–60 min for rapidly dissolving forms). The ergogenic effect begins at about 60% of peak concentration — which translates to a window of 40–120 minutes after consumption, peaking at 60 minutes (ISSN, 2021).
Practical rule: take a caffeine capsule 45–60 minutes before training. If you drink brewed coffee (slower absorption due to the coffee matrix), give yourself 60–90 minutes. For intense evening training, pay attention to the duration of the effect: the half-life of caffeine is 3–5 hours — shorter in individuals with a fast metabolism (CYP1A2 polymorphism), up to 8–9 hours in slow metabolizers. Training at 7:00 PM with a caffeine dose beforehand may hinder sleep until 11:00 PM or later.
Can you take caffeine on an empty stomach? Yes, caffeine absorbs better without food. However, for individuals with sensitive stomachs or reflux, an empty stomach increases the risk of irritation. A small meal (100–200 kcal) does not significantly change the absorption time and eliminates stomach discomfort.
From our observations, individuals trying caffeine supplementation for the first time often overdo the dose — taking 400–500 mg "because that’s what’s in the capsule", and then complaining about hand tremors and rapid heartbeat. Instead: start with 2 mg/kg, assess the effect over 2–3 weeks, and possibly increase to 3 mg/kg. Caution here really pays off.
Tolerance and how to reset it
Regular daily use of caffeine leads to adaptations of adenosine receptors — their density increases, which reduces the effect of the same dose. A study by Daly et al. showed that habitual caffeine consumers (over 400 mg/day for at least a week) did not achieve an ergogenic effect at a dose of 3 mg/kg, while those who do not regularly consume caffeine experienced a noticeable improvement (Daly et al., Psychopharmacology, 1981).
How to reset tolerance? ISSN recommends a 7-day break from caffeine before key competitions. During the first 2–4 days of the break, expect withdrawal symptoms: headaches, drowsiness, irritability. This is a normal physiological reaction — it will subside after a few days. It’s worth planning this reset before the most important events to restore full sensitivity to caffeine.
For whom might caffeine before training not be the best choice?
Caffeine is not for everyone. Several groups should exercise particular caution or avoid its pre-workout use. Firstly — individuals with hypertension, for whom caffeine may temporarily raise systolic blood pressure by 5–10 mmHg. Secondly — individuals with heart arrhythmias: caffeine increases heart rate and may trigger palpitations in predisposed individuals.
Thirdly — individuals training late in the evening. Caffeine taken at 7:00 PM by a slow metabolizer of CYP1A2 will still be active at 11:00 PM–12:00 AM, which will shorten sleep and reduce recovery. Poor sleep destroys training effects faster than a lack of caffeine. Fourthly — pregnant women: EFSA recommends limiting total caffeine intake to 200 mg/day during pregnancy. Supplementation before training within this limit is difficult to safely accommodate.
Frequently Asked Questions
How many mg of caffeine should I take before training?
According to ISSN, the minimum effective dose is 2 mg/kg of body weight, and a range of 3–6 mg/kg provides effects from submaximal to maximal. For a person weighing 75 kg, this means 150–450 mg of caffeine (ISSN, 2021). Doses above 6 mg/kg do not provide additional ergogenic benefits, and the risk of side effects increases. Start with 2 mg/kg and monitor your tolerance.
When should I take caffeine before training?
Caffeine in capsules reaches peak blood concentration 45–60 minutes after consumption. The optimal time is 45–60 minutes before training. Brewed coffee acts a bit slower — 60–90 minutes before. The ergogenic effect lasts 3–5 hours, depending on individual metabolism through the CYP1A2 enzyme.
Does tolerance to caffeine diminish the pre-workout effect?
Yes, regular daily caffeine consumption reduces its ergogenic effect due to the adaptation of adenosine receptors. The ISSN recommendation is to avoid caffeine for 3–7 days before competitions or key training sessions to restore receptor sensitivity (ISSN, 2021). The break is associated with withdrawal symptoms for several days.
Does caffeine work the same before strength and endurance training?
Yes, although the mechanisms differ slightly. In endurance training, caffeine slows the perception of fatigue by blocking adenosine. In strength training, a meta-analysis of 21 RCTs showed an improvement in maximum strength of 3–4% and repetitions to failure of 5–8% at doses of 3–6 mg/kg (Grgic et al., 2018). The effect is more pronounced for the upper body than the lower body.
Can I replace caffeine capsules with coffee before training?
Yes, coffee is an equivalent source of caffeine before training. The difference lies in dosing precision — the caffeine content in coffee varies (80–200 mg per 250 ml). Caffeine capsules provide an exact dose. The biological effect of caffeine is the same regardless of the source — choose the format that fits your training protocol.
This article is for informational and educational purposes and does not replace consultation with a doctor. If you are pregnant, breastfeeding, taking medications, or have chronic conditions, consult the use of supplements or herbs with a specialist.
Author: Michał Waluk · Published: 2026-05-04 · Updated: 2026-05-04
