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What does caffeine do before a workout?

Paul Hummel Last reviewed June 10, 2026 5 min read
What does caffeine do before a workout?
Quick answer

The European Food Safety Authority (EFSA) recommends a maximum daily intake of 400 milligrams of caffeine for healthy adults. Single doses should not exceed 200 milligrams.

What is caffeine?

Caffeine is a naturally occurring alkaloid found in coffee, tea, cocoa, and many dietary supplements. It is absorbed quickly, reaching peak plasma concentration roughly 30 to 60 minutes after intake. How fast you metabolize it varies widely — genetic differences in the CYP1A2 enzyme influence how quickly caffeine is broken down (Pickering & Kiely, 2018).

Chart: Caffeine: limits & content of sources

EFSA safety assessment

The European Food Safety Authority (EFSA, 2015) conducted a comprehensive review of caffeine and issued the following recommendations for healthy adults: no more than 400 milligrams per day in total, and no more than 200 milligrams in a single dose. Pregnant women should stay below 200 milligrams per day. In a randomized study, Drake et al. (2013) showed that a single 400-milligram dose of caffeine measurably reduces sleep quality even when taken six hours before bedtime.

Caffeine content of common sources

SourceCaffeine content
Cup of filter coffee (250 ml)approx. 90 mg
Espresso (double, 60 ml)approx. 130 mg
Pre-workout supplement100–300 mg

Individual differences and caveats

Regular intake leads to tolerance. Possible side effects of excessive consumption include restlessness, racing heart, sleep problems, and gastrointestinal discomfort. Individual tolerance varies considerably (Pickering & Kiely, 2018).

Caffeine isn't a dietary supplement in the strict sense — it's a naturally occurring compound. The EFSA recommendations cover total intake from all sources (coffee, tea, supplements, energy drinks).

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Related questions

Sources

  1. Grgic, J., et al. (2019). The influence of caffeine supplementation on resistance exercise: A review. Sports Medicine, 49(1). PubMed
  2. Guest, N. S., et al. (2021). ISSN position stand: caffeine and exercise performance. JISSN, 18:1. jissn.biomedcentral.com
  3. Southward, K., et al. (2018). The Effect of Acute Caffeine Ingestion on Endurance Performance: A Systematic Review and Meta-Analysis. Sports Medicine, 48(8). PubMed
  4. Drake, C., et al. (2013). Caffeine effects on sleep taken 0, 3, or 6 hours before going to bed. J Clin Sleep Med, 9(11). PubMed
  5. EFSA (2015). Scientific Opinion on the safety of caffeine. EFSA Journal, 13(5). efsa.europa.eu
A note on supplements: supplements are no substitute for a balanced diet, and whether one makes sense depends on your individual situation. This content is for general informational purposes only and is not medical advice. If you have a medical condition, are pregnant, or take medication, consult a qualified professional.