How Long Does Caffeine Last? Hour by Hour

Key takeaways

• You may feel caffeine for several hours. Half of it is gone after about 4 hours on average, with a range of 2 to 8 hours in adults (EFSA). About 3 percent is left after 20 hours at the average pace, or 40 hours at the slow end (our calculation).
• The only “5 hours” we traced to the FDA is an aside about adults in one FDA-approved label, for caffeine citrate, a drug for premature babies. The FDA’s own consumer page and the NHS insomnia page give no half-life at all.
• Smoking speeds up caffeine’s breakdown, while the pill and pregnancy slow it. In a study of 7 healthy volunteers, the antidepressant fluvoxamine stretched the half-life from 4.9 to 56 hours.
• For sleep, the dose counts at least as much as the timing (our reading). In a 2025 trial with 23 young men, 100 mg in capsules had no significant effect even 4 hours before bed, while 400 mg disrupted sleep even 12 hours before. A 2023 meta-analysis, based on statistical modeling, advises at least 8.8 hours for a 107 mg coffee, about an 8.5-ounce cup. For an 11 p.m. bedtime, that means a last cup of that size by 2:12 p.m. (our conversion). A US 12-ounce cup holds more. Closer to 200 mg, we’d stop by 9:48 a.m. (our conversion). On the pill, we’d stop earlier still and ask a doctor or pharmacist. If you’re pregnant, ask your doctor or midwife.
• Caffeine withdrawal typically starts 12 to 24 hours after the last dose and lasts 2 to 9 days.

Contents

1. How long does caffeine last? The short answer
2. How long does caffeine stay in your system?
3. Is caffeine’s half-life 4, 5 or 6 hours?
4. Why does caffeine last longer for some people?
5. How long before bed should you stop caffeine?
6. How long does caffeine withdrawal last?
7. Frequently asked questions

Dieser Artikel auf Deutsch: Wie lange wirkt Koffein? Stunde für Stunde

How long caffeine lasts depends on which clock you read: how long you feel it, or how long it stays in your body. The caffeine check in our sleep calculator works as a caffeine half-life calculator for your drinks. Choose a drink and how many, enter when you had it and your bedtime, then set the half-life slider. Its half-life setting runs from 2 to 8 hours, EFSA’s range for adults. If you’re on the pill, pregnant or taking certain drugs, such as the antidepressant fluvoxamine, your half-life can run longer, and the check will likely underestimate what’s left^1,2,3. Healthy adults can have half-lives over 8 hours too: in a 1983 study of 10 healthy young men, individual values ran from 2.7 to 9.9 hours⁴.

How long does caffeine last? The short answer

Caffeine can kick in 15 to 30 minutes after you drink it, and the effects may last for several hours, says Germany’s Federal Institute for Risk Assessment (BfR)⁵. It blocks the brain’s receptors for adenosine, a messenger that builds up while you’re awake. Sleep pressure is thought to rise along with it. With those receptors blocked, caffeine can make you more alert⁶. How long you feel it varies from person to person, and none of the studies we checked puts a number on it⁵. The half-life of caffeine, the time your body needs to clear half of it, is about 4 hours on average in adults, with a range of about 2 to 8 hours, according to the European Food Safety Authority (EFSA)¹. It can be far longer on the pill, in pregnancy or with some drugs.

How long does caffeine stay in your system?

By our calculation, 25 percent of a cup’s caffeine is still in you after 8 hours at EFSA’s average half-life of about 4 hours, and it takes about 20 hours to get down to 3 percent, or 40 hours at the slow end¹.

Every half-life removes half of what is left. Our example is one cup of brewed (filter) coffee, which the BfR puts at 90 mg in a 200 ml cup, about 7 fluid ounces⁵. In the US, the FDA lists 113 to 247 mg for a 12-ounce cup of regular brewed coffee, so your mug may hold more than our example⁸.

By our calculation, what’s left of the cup after 8 hours ranges from 6 to 45 mg (36 mg at the nonsmoker pace), and at the slow end, 50 percent of it is still in your body. The columns are EFSA’s fast, average and slow half-life values plus the 6.0-hour mean of 13 nonsmokers in a 1978 study^1,9.

This is our calculation, not a measurement. In our model the percentages are the same for any dose. At higher doses, though, breakdown can slow down as metabolic pathways saturate, according to a 2011 review of caffeine’s pharmacokinetics. Its abstract names no dose at which that starts¹⁰. For your own drinks and bedtime, use the caffeine check. It adds up several cups of one kind drunk at the same time, and its half-life setting covers EFSA’s 2 to 8 hours¹. For cups spread over the day, run it once per cup and add up what’s left.

Is caffeine’s half-life 4, 5 or 6 hours?

EFSA says about 4 hours (range 2 to 8)¹. Among official sources, we found a flat 5 hours only as an aside in a US drug label and 5 to 6 on an archived CDC training page^11,12. That label is for caffeine citrate, a drug for breathing pauses in premature babies, and its 5-hour figure refers to adults¹¹. Another FDA-approved label says about 3 hours¹³.

The FDA’s consumer page on caffeine gives no half-life at all. It says people vary widely in how fast they eliminate caffeine⁸. A 2007 FDA consumer brochure (archived copy) says caffeine usually peaks in the blood within an hour and “stays there for four to six hours,” with no source for that figure¹⁴. That is not a half-life, whether “there” means the peak level or simply the bloodstream. If it means the peak, it doesn’t fit the measured half-lives either, because at a half-life of about 4 hours the level is down to about half 4 hours after the peak (our calculation)¹.

No NHS page we found says 5 hours, the figure on the caffeine citrate label¹¹. The national insomnia page gives no half-life, while local pages of NHS hospital trusts say 4 to 6 hours or that caffeine “halves every four hours” in the body^15,16,17.

Most of the top-ranking pages we checked name no source for their number. The studies that do measure half-lives tested different people, and smoking is one clear reason their results differ. In a 1978 study, 13 smokers averaged 3.5 hours and 13 nonsmokers 6.0⁹. Healthy volunteers’ control values in other small studies ran from 4.9 to 6.2 hours^2,3,18,19, while a 1981 study of 25 nonpregnant adults found 3.4 hours. Its abstract does not say who smoked, and it is one of the studies EFSA cites for its 4-hour figure^1,20. All of these fall inside EFSA’s range of 2 to 8 hours, but most healthy-group averages sit above EFSA’s 4 hours, so when in doubt, assume a longer half-life.

Why does caffeine last longer for some people?

The pill and pregnancy slow caffeine’s breakdown¹⁰, and some medications and severe liver disease can stretch the half-life from hours to days^3,18. Smoking has the opposite effect and speeds up the breakdown⁹. Sex alone changes little¹⁰. About 95 percent of caffeine’s clearance runs through one liver enzyme, CYP1A2¹. A review adds obesity, diet and CYP1A2 gene variants, but none of our sources gives a half-life per variant²¹.

In one study of 7 volunteers, fluvoxamine kept a single 250 mg dose in the body far longer without stronger effects on alertness or performance. Sleep was not measured³. The authors do not rule out harm from caffeine piling up with daily intake³. A second study, in 8 volunteers whose median half-life rose from 5 to 31 hours, warns that caffeine taken during fluvoxamine treatment may lead to caffeine intoxication¹⁹. If you take fluvoxamine or other regular medication, ask your doctor or pharmacist about caffeine.

How long before bed should you stop caffeine?

For about 100 mg of caffeine, roughly an 8.5-ounce (250 ml) cup of brewed coffee, the cutoffs we found run from 4 hours, in a 2025 trial of young men given capsules, to 8.8 hours, in a 2023 meta-analysis^6,25. A US 12-ounce cup holds more⁸. If yours is closer to 200 mg, we’d go by the meta-analysis’s 13.2-hour cutoff for a 217.5 mg pre-workout serving²⁵. For even more at once, above the 200 mg single dose that EFSA found raises no safety concerns for healthy adults, our sources give only minimums¹. The authors of a 2013 trial, described below, say that at a minimum, afternoon caffeine should end before 5 p.m., particularly in moderate to large doses²⁶. The 2025 trial’s authors advise against 400 mg within 12 hours of bedtime, and in their trial a single 400 mg dose still disturbed sleep at 12 hours, the longest gap they tested⁶. Both allow less time than the 13.2 hours above, so even with more caffeine, we’d stop no later than 13.2 hours before bed (our reading). EFSA notes that single doses of about 100 mg can delay and shorten sleep when taken close to bedtime¹.

In a 2013 trial, 12 healthy normal sleepers, young or middle-aged moderate caffeine users, took 400 mg in pill form on different days: at bedtime, 3 hours before or 6 hours before, with only a placebo on another day²⁶. A sleep monitor recorded 1.1 to 1.2 hours less sleep than with a placebo each time, more than 1 hour even at 6 hours²⁶. At 6 hours, their diaries showed 41 minutes less, short of statistical significance²⁶.

A 2023 meta-analysis of 24 studies found that caffeine cut total sleep by 45 minutes and sleep efficiency by 7 percent, and added 9 minutes to falling asleep and 12 minutes awake at night²⁵. It advises having a 107 mg coffee (250 ml) at least 8.8 hours before bed and a 217.5 mg pre-workout serving at least 13.2 hours before²⁵.

In a 2025 trial, several of the same researchers put each of 23 young men with a moderate caffeine habit through every condition: a placebo and 100 or 400 mg in capsules at 12, 8 or 4 hours before bed. The authors note that 100 mg is about one cup of coffee⁶. The 100 mg dose had no significant effect on sleep. The 400 mg dose did, more so the closer to bedtime⁶. The men rated their sleep quality worse only when the 400 mg came 4 hours before bed. At 8 hours they still reported sleeping about 0.7 hours less, and at 12 hours they noticed no significant change even though the measurements still showed changed sleep stages⁶. The team notes that the 8.8 hours came from statistical modeling and that results in young men may not apply to everyone⁶.

Our take: how you feel is the wrong clock. In both trials, people noticed the damage when the dose came close to bedtime, but less and less as it moved earlier in the day. In the 2013 trial, when 400 mg came 6 hours before bed, the diaries logged only 41 minutes lost, not a significant change, while the monitor measured more than an hour. In the 2025 trial, the men’s own estimates of time awake at night showed no significant change after 400 mg at 4 or 8 hours, although the measurements did, and the authors say people may have difficulty perceiving caffeine’s effect on their sleep quality^6,26.

The caffeine check shows what your own drinks leave at bedtime and compares it with EFSA’s figure of about 100 mg for a single dose close to bedtime¹. If 100 mg or more would be left at bedtime, it also tells you by when you would have needed to finish the drink for less than 100 mg to be left. That is all this time tells you. For sleep, we’d go by the times in the table above. For more than 200 mg at once within 12 hours of bedtime, it gives no such time and shows the 2025 trial’s result instead of the 100 mg comparison, because a low remainder doesn’t mean a big dose won’t disturb your sleep⁶. We chose the 200 mg line for the tool because EFSA found that single doses up to that amount raise no safety concerns for healthy adults¹.

If you are over 40 or a woman, we’d go by the meta-analysis column, not the 2025 trial’s. The trial studied only young men. Its authors point to evidence that caffeine disturbs sleep more in adults over 40 and note that hormones may play a role in women⁶. On the pill, we’d plan earlier still. In one study, the half-life averaged 10.7 hours vs. 6.2 without it, and no study we checked set a cutoff for pill users, so ask your doctor or pharmacist². In pregnancy, EFSA reports half-lives of 6 to 16 hours in 15 pregnant women and 3 to 4 times the usual by the end of pregnancy¹. No study we checked set a cutoff for pregnant women, so ask your doctor or midwife.

In the 2025 trial, 100 mg in a capsule taken 4 hours before bed had no significant effect on young men’s sleep, which for an 11 p.m. bedtime would be 7 p.m. (our conversion)⁶. For a cup with about 100 mg, the meta-analysis cutoff works out to 2:12 p.m. (our conversion), and that is the time we’d plan around if you are over 40 or a woman^6,25.

How long does caffeine withdrawal last?

Usually 2 to 9 days. A 2004 review found that symptoms typically start 12 to 24 hours after the last dose and peak at 20 to 51 hours²⁷. Ten symptoms met the review’s validity criteria: headache, fatigue, low energy, lower alertness, drowsiness, feeling less content, depressed mood, trouble concentrating, irritability and brain fog²⁷. In experiments, 50 percent of people got a headache and 13 percent had clinically significant distress or impairment²⁷. Even quitting a habit of 100 mg a day could trigger symptoms, and higher doses generally made them more likely or more severe²⁷. If you want to cut back, the FDA advises doing it gradually⁸.

Frequently asked questions

How long does it take for caffeine to kick in?

About 30 minutes, with a range of 15 to 45, says NIOSH, part of the CDC. The BfR says effects can start 15 to 30 minutes after you drink it^5,12. In 13 regular drinkers given 400 mg, saliva levels peaked 42 minutes after coffee, 39 after cola and 67 after capsules, and coffee and cola did not appear to differ in absorption or felt effects⁷.

How long does 200 mg (or 100 or 80 mg) of caffeine last?

Half of 200 mg is gone after about 4 hours on average (EFSA). By our calculation, 50 mg is left after 8 hours and about 6 mg after 20 hours (40 hours at the slow end). Of 100 mg, 25 mg is left after 8 hours, and of an 80 mg espresso or energy drink (BfR servings), 20 mg^1,5. For scale, 100 mg is about one cup of coffee in the 2025 trial’s terms⁶. Our sources put no number of hours on how long you’d feel it. The BfR says only that the effects may last several hours⁵.

Can you flush caffeine out of your system faster?

Not in any healthy way our sources support, and by our reading extra water barely helps, because your liver sets the pace. Less than 2 percent of caffeine leaves your body unchanged in urine¹⁰, and a single liver enzyme, CYP1A2, handles about 95 percent of its clearance¹. A review’s abstract lists exercise and foods such as broccoli among the influences on how caffeine is eliminated, without saying which way or how much they change it¹⁰. Among adults, smoking is the only factor in the studies we checked that clearly sped up clearance, and we’re not suggesting you smoke⁹.

How much caffeine a day is considered safe?

For healthy adults, EFSA concluded that up to 400 mg a day from all sources, spread over the day, and single doses up to 200 mg “do not give rise to safety concerns.” Pregnant women are the exception¹. That is a safety assessment, not a recommended amount, and the BfR notes that EFSA’s figures do not apply to people who are ill, take medication or drink large amounts of alcohol⁵. The FDA cites the same 400 mg a day, about two to three 12-ounce cups of coffee⁸.

Is caffeine safe for children and teens?

It depends on age and amount. In the US, the Dietary Guidelines for Americans say children under 2 should avoid caffeinated drinks, and the American Academy of Pediatrics advises against energy drinks for children and teens because of their sugar and caffeine⁸. In the EU, EFSA considered 3 mg of caffeine per kilogram of body weight (about 1.4 mg per pound), taken at once or over the day, not to be associated with negative effects in healthy children and teens, according to Germany’s BfR⁵.

Does caffeine last longer during pregnancy?

Yes, much longer. EFSA reports half-lives of 6 to 16 hours in 15 pregnant women, and 3 to 4 times the usual by the end of pregnancy¹. A 1981 study of 57 pregnant women measured 8.3 hours on average²⁰. EFSA’s safety figure for pregnancy is up to 200 mg a day, and according to the BfR’s summary of EFSA’s assessment, the same 200 mg holds while breastfeeding^1,5. In the US, the FDA recommends talking to your health care provider about whether to limit caffeine if you’re pregnant, trying to become pregnant or breastfeeding⁸.

Sources

1. EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA). Scientific Opinion on the safety of caffeine. EFSA Journal 2015;13(5):4102. doi:10.2903/j.efsa.2015.4102 (retrieved August 28, 2026)
2. Patwardhan RV, Desmond PV, Johnson RF, Schenker S. Impaired elimination of caffeine by oral contraceptive steroids. J Lab Clin Med 1980;95(4):603-608. pubmed.ncbi.nlm.nih.gov/7359014 (retrieved September 29, 2026)
3. Culm-Merdek KE, von Moltke LL, Harmatz JS, Greenblatt DJ. Fluvoxamine impairs single-dose caffeine clearance without altering caffeine pharmacodynamics. Br J Clin Pharmacol 2005;60(5):486-493. doi:10.1111/j.1365-2125.2005.02467.x (retrieved September 29, 2026)
4. Blanchard J, Sawers SJ. The absolute bioavailability of caffeine in man. Eur J Clin Pharmacol 1983;24(1):93-98. doi:10.1007/BF00613933 (retrieved September 29, 2026)
5. German Federal Institute for Risk Assessment (BfR). Coffee, energy drinks and caffeine powder: Energizers with health risks? FAQ. Published 2026. bfr.bund.de/en/release/frequently-asked-questions-on-caffeine-and-foods-containing-caffeine-including-energy-drinks (retrieved September 29, 2026)
6. Gardiner CL, Weakley J, Burke LM, Fernandez F, Johnston RD, Leota J, Russell S, Munteanu G, Townshend A, Halson SL. Dose and timing effects of caffeine on subsequent sleep: a randomized clinical crossover trial. Sleep 2025;48(4):zsae230. doi:10.1093/sleep/zsae230 (retrieved September 29, 2026)
7. Liguori A, Hughes JR, Grass JA. Absorption and subjective effects of caffeine from coffee, cola and capsules. Pharmacol Biochem Behav 1997;58(3):721-726. doi:10.1016/s0091-3057(97)00003-8 (retrieved September 29, 2026)
8. U.S. Food and Drug Administration (FDA). Spilling the Beans: How Much Caffeine is Too Much? Consumer update, content current as of August 28, 2024. fda.gov/consumers/consumer-updates/spilling-beans-how-much-caffeine-too-much (retrieved September 29, 2026)
9. Parsons WD, Neims AH. Effect of smoking on caffeine clearance. Clin Pharmacol Ther 1978;24(1):40-45. doi:10.1002/cpt197824140 (retrieved September 29, 2026)
10. Arnaud MJ. Pharmacokinetics and metabolism of natural methylxanthines in animal and man. Handb Exp Pharmacol 2011;(200):33-91. doi:10.1007/978-3-642-13443-2_3 (retrieved September 29, 2026)
11. Caffeine Citrate Injection, USP / Caffeine Citrate Oral Solution, USP. Prescribing information, Sagent Pharmaceuticals. FDA-approved labeling, DailyMed SPL setid 5f38c395-0093-4afd-89ec-f96e5dc0934a, effective July 29, 2026. dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=5f38c395-0093-4afd-89ec-f96e5dc0934a (retrieved September 29, 2026)
12. National Institute for Occupational Safety and Health (NIOSH), CDC. Caffeine & Long Work Hours. Interim NIOSH Training for Emergency Responders: Reducing Risks Associated with Long Work Hours, page 39 of 48. Last reviewed April 1, 2020 (archived page). archive.cdc.gov/www_cdc_gov/niosh/emres/longhourstraining/caffeine.html (retrieved September 29, 2026)
13. Butalbital, Acetaminophen and Caffeine Oral Solution. Prescribing information, Genus Lifesciences. FDA-approved labeling, DailyMed SPL setid 5f603b0d-69e5-4c02-b6b3-b4705e243e9a, effective September 25, 2026. dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=5f603b0d-69e5-4c02-b6b3-b4705e243e9a (retrieved September 29, 2026)
14. U.S. Food and Drug Administration (FDA). Medicines in my Home: Caffeine and Your Body. Consumer brochure, originally published fall 2007 (archived copy). web.archive.org/web/20170501120709id_/https://www.fda.gov/downloads/UCM200805.pdf (retrieved September 29, 2026)
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22. Joeres R, Klinker H, Heusler H, Epping J, Zilly W, Richter E. Influence of smoking on caffeine elimination in healthy volunteers and in patients with alcoholic liver cirrhosis. Hepatology 1988;8(3):575-579. doi:10.1002/hep.1840080323 (retrieved September 29, 2026)
23. Scott NR, Stambuk D, Chakraborty J, Marks V, Morgan MY. Caffeine clearance and biotransformation in patients with chronic liver disease. Clin Sci (Lond) 1988;74(4):377-384. doi:10.1042/cs0740377 (retrieved September 29, 2026)
24. Blanchard J, Sawers SJ. Comparative pharmacokinetics of caffeine in young and elderly men. J Pharmacokinet Biopharm 1983;11(2):109-126. doi:10.1007/BF01061844 (retrieved September 29, 2026)
25. Gardiner C, Weakley J, Burke LM, Roach GD, Sargent C, Maniar N, Townshend A, Halson SL. The effect of caffeine on subsequent sleep: A systematic review and meta-analysis. Sleep Med Rev 2023;69:101764. doi:10.1016/j.smrv.2023.101764 (retrieved September 29, 2026)
26. Drake C, Roehrs T, Shambroom J, Roth T. Caffeine effects on sleep taken 0, 3, or 6 hours before going to bed. J Clin Sleep Med 2013;9(11):1195-1200. doi:10.5664/jcsm.3170 (retrieved September 29, 2026)
27. Juliano LM, Griffiths RR. A critical review of caffeine withdrawal: empirical validation of symptoms and signs, incidence, severity, and associated features. Psychopharmacology (Berl) 2004;176(1):1-29. doi:10.1007/s00213-004-2000-x (retrieved September 29, 2026)

Published October 10, 2026 · Last updated October 10, 2026 · Wild Garden Editorial Team · Last verified October 10, 2026 · 121 of 121 source citations confirmed against the primary source · Our editorial standards · Spotted an error? redaktion@wildgarden.io

This article is not medical advice. If symptoms persist, if you are pregnant or if you take medication, talk to a doctor.

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The sleep calculator also lays out your bedtimes in sleep cycles. If your mind races at night, the breathing exercise timer paces each exercise the way the health sources it cites describe it. And if an earlier last coffee is the plan, the habit formation calculator shows how long new habits took to stick in a real-life study.

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