Caffeine is the most widely-used stimulant in the world. It’s found in coffee, tea, soda, energy drinks, and energy shots, as well as some sports gels, dietary supplements, over-the-counter medications, and combat ration items (pudding, gum, and mints). In moderate doses, caffeine can boost both physical and mental performance. As with other stimulants, though, too much caffeine can have negative consequences, so it’s important to be aware of how much caffeine you’re consuming, and use it appropriately and strategically. Dietary supplements sometimes have significant amounts of caffeine, which adds to your daily intake, so pay special attention to what’s on the labels.

How much caffeine is safe?

For healthy adults, including women who are not pregnant or lactating, up to 400 mg per day of caffeine is considered safe. Less than that isn’t likely to lead to serious side effects. However, sensitivity to caffeine differs from person to person. Side effects include headaches, dizziness, nervousness, restlessness, and trouble sleeping. More serious side effects can occur with higher doses. In fact, 150–200 mg/kg bodyweight—or about 10–14 grams for the average person—can be fatal. This amount might seem difficult to achieve, but pure and highly concentrated caffeine are readily available and sold as dietary supplements, which the Food and Drug Administration (FDA) warns against because it’s up to you as the consumer to accurately measure out a serving. And, according to FDA, one teaspoon of pure powdered caffeine contains as much caffeine as 28 cups of coffee.

If I use caffeine for performance, how much should I use?

Caffeine can help improve some, but not all, measures of cognitive performance, such as vigilance, attention, and alertness, during long activities such as patrolling at night or when you are sleep deprived. For physical performance, caffeine works better for endurance rather than for short-term, high-intensity, or strength activities.

The exact amount of caffeine that can help performance varies among indviduals, and some respond better than others. In general, up to 200 mg (about the amount of caffeine in 8–12 oz of brewed coffee) at any one time is appropriate. Consume caffeine about 30–60 minutes before a workout, training session, work shift, or mission for best results, as it takes about an hour to reach peak blood levels. That also means you might need another dose of caffeine after 3–4 hours to help you stay alert or active for a long period of time. However, add up all the sources of caffeine in your diet and do not exceed 600 mg of caffeine per day (800 mg for sustained operations) to minimize risk of side effects.

How can I tell if my supplement contains caffeine?

If your supplement is marketed for weight loss, energy, or pre-workout, it probably contains caffeine. To see if your supplement contains caffeine, look at the Supplement Facts panel. Caffeine is often listed simply as “caffeine,” but various forms or terms include “caffeine anhydrous,” 1,3,7-trimethylxanthine, and others.

Other times the caffeine might be “hidden” in an ingredient. Sources of caffeine include:

  • Cocoa (cacao, Theobroma cacao)
  • Coffee or coffea
  • Green coffee bean
  • Guarana
  • Kola nut
  • Methylxanthine
  • Tea (Camellia sinesis)
  • Trimethylxanthine
  • Xanthine
  • Yerba maté

The total amount of caffeine might be listed on the Supplement Facts panel. If the caffeine is included in a “proprietary blend,” you might not be able to tell from looking at the Supplement Facts panel how much caffeine is in a serving. The amount of caffeine might be listed elsewhere on the container, so be sure to read the entire product label. Regardless, when looking at labels, look for the total amount of caffeine per serving in the product and factor it into your total daily caffeine intake.

What else should I know about caffeine?

While caffeine can improve how you perform, there are a few things you should keep in mind:

  • If you do choose to use caffeine, make sure you try it before an event or mission to assess your tolerability. Caffeine can provide some benefit, but it’s not a necessity.
  • More caffeine will not improve your performance, and the various negative side effects of higher doses might actually make it worse.
  • Try to avoid caffeine for at least 6 hours before bedtime to make sure it doesn't interfere with your sleep.
  • Caffeine can boost mental performance, but it’s not a substitute for sleep.
  • Be aware too of supplements containing caffeine along with other stimulants because there’s limited information about the safety of combining such ingredients.

For additional information about caffeine:

Updated 26 February 2019

References

2015 Dietary Guidelines Advisory Committee. (2015). Key Elements of Healthy Eating Patterns: Caffeine Dietary Guidelines for Americans, 2015–2020 (8th ed.). Washington, DC: Department of Health and Human Services & U.S. Department of Agriculture.

Administration, U. S. F. D. (2018, 21 September 2018). Pure and highly concentrated caffeine. Retrieved 26 February 2019 from https://www.fda.gov/food/dietarysupplements/productsingredients/ucm460095.htm

Astorino, T. A., & Roberson, D. W. (2010). Efficacy of acute caffeine ingestion for short-term high-intensity exercise performance: A systematic review. Journal of Strength and Conditioning Research, 24(1), 257–265. doi:10.1519/JSC.0b013e3181c1f88a

Bell, D. G., & McLellan, T. M. (2002). Exercise endurance 1, 3, and 6 h after caffeine ingestion in caffeine users and nonusers. Journal of Applied Physiology, 93(4), 1227–1234. doi:10.1152/japplphysiol.00187.2002

Bell, D. G., & McLellan, T. M. (2003). Effect of repeated caffeine ingestion on repeated exhaustive exercise endurance. Medicine & Science in Sports & Exercise, 35(8), 1348–1354. doi:10.1249/01.Mss.0000079071.92647.F2

Burke, L. M. (2008). Caffeine and sports performance. Applied Physiology, Nutrition, and Metabolism, 33(6), 1319–1334. doi:10.1139/h08-130

Cappelletti, S., Daria, P., Sani, G., & Aromatario, M. (2015). Caffeine: Cognitive and physical performance enhancer or psychoactive drug? Current Neuropharmacology, 13(1), 71–88. doi:10.2174/1570159x13666141210215655

Christensen, P. M., Shirai, Y., Ritz, C., & Nordsborg, N. B. (2017). Caffeine and bicarbonate for speed. A meta-analysis of legal supplements potential for improving intense endurance exercise performance. Frontiers in Physiology, 8, 587–596. doi:10.3389/fphys.2017.00240

Cox, G. R., Desbrow, B., Montgomery, P. G., Anderson, M. E., Bruce, C. R., Macrides, T. A., . . . Burke, L. M. (2002). Effect of different protocols of caffeine intake on metabolism and endurance performance. Journal of Applied Physiology, 93(3), 990–999. doi:10.1152/japplphysiol.00249.2002

Crawford, C., Teo, L., Lafferty, L., Drake, A., Bingham, J. J., Gallon, M. D., . . . Berry, K. (2017). Caffeine to optimize cognitive function for military mission-readiness: A systematic review and recommendations for the field. Nutrition Reviews, 75(suppl_2), 17–35. doi:10.1093/nutrit/nux007

Department of the Army Headquarters. (2016). A Leader’s Guide to Soldier Health and Fitness. Department of the Army, Washington, DC, Retrieved from: https://armypubs.army.mil/epubs/DR_pubs/DR_a/pdf/web/atp6_22x5.pdf

Earnest, C. P., Hodgson, A. B., Randell, R. K., & Jeukendrup, A. E. (2013). The metabolic and performance effects of caffeine compared to coffee during endurance exercise. PLoS ONE, 8(4). doi:10.1371/journal.pone.0059561

Gillingham, R. L., Keefe, A. A., & Tikulsis, P. (2004). Acute caffeine intake before and after fatiguing exercise improves target shooting engagement time. Aviation, Space, and Environmental Medicine, 75(10), 865–871.

Goldstein, E. R., Ziegenfuss, T., Kalman, D., Kreider, R., Campbell, B., Wilborn, C., . . . Antonio, J. (2010). International society of sports nutrition position stand: caffeine and performance. Journal of the International Society of Sports Nutrition, 7(1), 7. doi:10.1186/1550-2783-7-5

Grgic, J. (2017). Caffeine ingestion enhances Wingate performance: A meta-analysis. European Journal of Sport Science, 18(2), 219–225. doi:10.1080/17461391.2017.1394371

Grgic, J., Trexler, E. T., Lazinica, B., & Pedisic, Z. (2018). Effects of caffeine intake on muscle strength and power: a systematic review and meta-analysis. Journal of the International Society of Sports Nutrition, 15(1), 11. doi:10.1186/s12970-018-0216-0

Hewlett, P., & Smith, A. (2007). Effects of repeated doses of caffeine on performance and alertness: new data and secondary analyses. Human Psychopharmacology: Clinical and Experimental, 22(6), 339–350. doi:10.1002/hup.854

Institute of Medicine (US) Committee on Military Nutrition Research. (2001). Caffeine for the Sustainment of Mental Task Performance: Formulations for Military Operations. Washington, DC: National Academies Press.

Jenkins, N. T., Trilk, J. L., Singhal, A., O’Connor, P. J., & Cureton, K. J. (2008). Ergogenic effects of low doses of caffeine on cycling performance. International Journal of Sport Nutrition and Exercise Metabolism, 18(3), 328–342.

Kamimori, G. H., McLellan, T. M., Tate, C. M., Voss, D. M., Niro, P., & Lieberman, H. R. (2014). Caffeine improves reaction time, vigilance and logical reasoning during extended periods with restricted opportunities for sleep. Psychopharmacology, 232(12), 2031–2042. doi:10.1007/s00213-014-3834-5

Lieberman, H., Tharion, W., Shukitt-Hale, B., Speckman, K., & Tulley, R. (2002). Effects of caffeine, sleep loss, and stress on cognitive performance and mood during U.S. Navy SEAL training. Psychopharmacology, 164(3), 250–261. doi:10.1007/s00213-002-1217-9

McLellan, T. M., Bell, D. G., & Kamimori, G. H. (2004). Caffeine improves physical performance during 24 h of active wakefulness. Aviation, Space, and Environmental Medicine, 75(8), 666–672.

McLellan, T. M., Caldwell, J. A., & Lieberman, H. R. (2016). A review of caffeine’s effects on cognitive, physical and occupational performance. Neuroscience & Biobehavioral Reviews, 71, 294–312. doi:10.1016/j.neubiorev.2016.09.001

McLellan, T. M., Kamimori, G. H., Bell, D. G., Smith, I. F., Johnson, D., & Belenky, G. (2005). Caffeine maintains vigilance and marksmanship in simulated urban operations with sleep deprivation. Aviation, Space, and Environmental Medicine, 76(1), 39–45.

McLellan, T. M., Kamimori, G. H., Voss, D. M., Bell, D. G., Cole, K. G., & Johnson, D. (2005). Caffeine maintains vigilance and improves run times during night operations for Special Forces. Aviation, Space, and Environmental Medicine, 76(7), 647–654.

McLellan, T. M., Kamimori, G. H., Voss, D. M., Tate, C., & Smith, S. J. (2007). Caffeine effects on physical and cognitive performance during sustained operations. Aviation, Space, and Environmental Medicine, 78(9), 871–877.

MedlinePlus. (2015, 22 February 2019). Caffeine. Retrieved 26 February 2019 from https://medlineplus.gov/caffeine.html

Richardson, D. L., & Clarke, N. D. (2016). Effect of coffee and caffeine ingestion on resistance exercise performance. Journal of Strength and Conditioning Research, 30(10), 2892–2900. doi:10.1519/jsc.0000000000001382

Southward, K., Rutherfurd-Markwick, K. J., & Ali, A. (2018). The effect of acute caffeine ingestion on endurance performance: A systematic review and meta–analysis. Sports Medicine, 48(8), 1913–1928. doi:10.1007/s40279-018-0939-8

Spriet, L. L. (2014). Exercise and sport performance with low doses of caffeine. Sports Medicine, 44(S2), 175–184. doi:10.1007/s40279-014-0257-8

Talanian, J. L., & Spriet, L. L. (2016). Low and moderate doses of caffeine late in exercise improve performance in trained cyclists. Applied Physiology, Nutrition, and Metabolism, 41(8), 850–855. doi:10.1139/apnm-2016-0053

Tarnopolsky, M. A. (2010). Caffeine and creatine use in sport. Annals of Nutrition and Metabolism, 57(s2), 1–8. doi:10.1159/000322696

Temple, J. L., Bernard, C., Lipshultz, S. E., Czachor, J. D., Westphal, J. A., & Mestre, M. A. (2017). The safety of ingested caffeine: A comprehensive review. Frontiers in Psychiatry, 8, 80. doi:10.3389/fpsyt.2017.00080

Temple, J. L., Hostler, D., Martin-Gill, C., Moore, Charity G., Weiss, P. M., Sequeira, D. J., . . . Patterson, P. D. (2018). Systematic review and meta-analysis of the effects of caffeine in fatigued shift workers: Implications for emergency medical services personnel. Prehospital Emergency Care, 22(sup1), 37–46. doi:10.1080/10903127.2017.1382624

Tharion, W. J., Shukitt-Hale, B., & Lieberman, H. R. (2003). Caffeine effects on marksmanship during high-stress military training with 72 hour sleep deprivation. Aviation, Space, and Environmental Medicine, 74(4), 309–314.

Tikulsis, P., Keefe, A. A., McLellan, T. M., & Kamimori, G. (2004). Caffeine restores engagement speed but not shooting precision following 22 h of active wakefulness. Aviation, Space, and Environmental Medicine, 75(9), 771–776.

U. S. Food & Drug Administration. (2018, 15 September 2018). Guidance for industry: Highly concentrated caffeine in dietary supplements. Retrieved 26 February 2019 from https://www.fda.gov/Food/GuidanceRegulation/GuidanceDocumentsRegulatoryInformation/ucm604318.htm

Wikoff, D., Welsh, B. T., Henderson, R., Brorby, G. P., Britt, J., Myers, E., . . . Doepker, C. (2017). Systematic review of the potential adverse effects of caffeine consumption in healthy adults, pregnant women, adolescents, and children. Food and Chemical Toxicology, 109, 58–-648. doi:10.1016/j.fct.2017.04.002