How long does caffeine last in your system?
Caffeine kicks in within 15–45 minutes and has a half-life of about 5 hours: half a dose is left after 5 hours, a quarter after 10, and it clears in a day.
Caffeine is absorbed quickly and almost completely from the gut. Most people feel it within 15–45 minutes, and blood concentration peaks around 45 minutes after a coffee or a capsule. From there it is cleared at a steady proportional rate, with a half-life of about five hours in a typical adult: half the dose is gone after five hours, three-quarters after ten, and after about a day — five half-lives — roughly 3% remains, which is effectively out of your system.
Two different questions hide inside "how long does caffeine last". How long you feel it and how long it stays in your body are not the same. Most people notice the alertness fading after three to five hours, as concentration falls well below its peak, but the caffeine is still there and still acting on sleep. Half of a 2pm coffee is in your bloodstream at 7pm, and a quarter of it at midnight.
The five-hour figure is an average. Healthy adults range from roughly three to seven hours, mostly because of genetic differences in CYP1A2, the liver enzyme that does almost all of the work. Smoking speeds that enzyme up and can roughly halve the half-life; oral contraceptives slow it and can roughly double it; in late pregnancy it can exceed ten hours. Coffee, tea, cola, energy drinks, gels and tablets all deliver the same molecule and are cleared the same way — what differs is how much each one contains.
For racing, the long half-life is convenient. A dose of 3–6 mg per kilogram taken 45–60 minutes before the start peaks near the gun and is still mostly present 30 km later, when perceived exertion is highest, so there is no need to time a second dose. The cost runs the other way: caffeine taken before an evening session is still about half present at bedtime, and it disrupts sleep even when you fall asleep normally — a poor trade in a heavy training block.
Key numbers
| Takes effect | 15–45 min | after a drink or capsule |
|---|---|---|
| Peak level | ~45 min | after ingestion |
| Half-life | ~5 hours | typical adult; 3–7 h range |
| Cleared | ~24 hours | about 3% of the dose left |
How much caffeine is left, by dose
| Dose | After 5 h | After 10 h | After 15 h | After 24 h |
|---|---|---|---|---|
| 100 mg (about one coffee) | 50 mg | 25 mg | 13 mg | 4 mg |
| 200 mg (two coffees) | 100 mg | 50 mg | 25 mg | 7 mg |
| 300 mg (4 mg/kg at 75 kg) | 150 mg | 75 mg | 38 mg | 11 mg |
| 400 mg (adult daily limit) | 200 mg | 100 mg | 50 mg | 14 mg |
Assumes the typical 5-hour half-life, counted from the peak about 45 minutes after you take it. A fast metaboliser clears it sooner; a slow one carries considerably more, especially late in the day. 400 mg a day is the EFSA safe-intake level for healthy adults.
Caffeine in common drinks and products
| Source | Typical caffeine |
|---|---|
| Brewed coffee, 240 mL (8 oz) | ~95 mg |
| Espresso, single shot | ~63 mg |
| Instant coffee, one cup | ~60 mg |
| Black tea, 240 mL (8 oz) | ~47 mg |
| Green tea, 240 mL (8 oz) | ~28 mg |
| Cola, 355 mL can | ~34 mg |
| Energy drink, 250 mL can | ~80 mg |
| Caffeinated energy gel | 20–100 mg |
| Caffeine tablet | 100–200 mg |
Typical values from USDA FoodData Central. Brewed coffee varies from roughly 70 to 140 mg a cup with bean, grind and strength; gels vary most of all, so check the label.
Work it out for yourself
Caffeine & stimulants model — Plot the full absorption and elimination curve for your dose and timing.
Frequently asked questions
How long does it take for caffeine to kick in?
Most people feel it within 15–45 minutes, and blood levels peak around 45 minutes after a coffee or capsule. Caffeinated gum is absorbed partly through the lining of the mouth and acts somewhat faster. That peak is why race-day caffeine is usually taken 45–60 minutes before the start.
How long does 200 mg of caffeine last?
With a typical five-hour half-life, about 100 mg is still in your system five hours after the peak, 50 mg after ten hours and around 7 mg after a day. Most people stop feeling it after three to five hours, but it keeps affecting sleep for longer than that.
How long until caffeine wears off?
The noticeable lift usually fades after three to five hours. Clearing it from your body takes far longer: about five half-lives, or roughly a day, before only a few percent remains.
Does caffeine from tea last longer than caffeine from coffee?
No. It is the same molecule with the same half-life. A cup of black tea simply contains about half the caffeine of a cup of brewed coffee, so there is less of it to clear.
Can you flush caffeine out of your system faster?
Not meaningfully. Almost all of it is broken down by one liver enzyme at its own rate; drinking water, exercising or eating does not speed that up. The only reliable option is time.
When should I stop drinking coffee before bed?
Given a five-hour half-life, a dose at 3pm is still roughly a quarter present at 1am. In a controlled study, 400 mg taken even six hours before bed cut total sleep by more than an hour, so most guidance puts the cut-off eight to ten hours before bed — considerably earlier than most people assume.
Why does caffeine affect some people more than others?
Largely genetics. Variation in the CYP1A2 enzyme produces fast and slow metabolisers with substantially different elimination rates, and adenosine receptor differences affect sensitivity independently of metabolism.
Sources
- Fredholm, Bättig, Holmén, Nehlig & Zvartau (1999). Actions of caffeine in the brain with special reference to factors that contribute to its widespread use. Pharmacological Reviews.
- Nehlig (2018). Interindividual differences in caffeine metabolism and factors driving caffeine consumption. Pharmacological Reviews.
- Kamimori et al. (2002). The rate of absorption and relative bioavailability of caffeine administered in chewing gum versus capsules to normal healthy volunteers. International Journal of Pharmaceutics.
- Drake, Roehrs, Shambroom & Roth (2013). Caffeine effects on sleep taken 0, 3, or 6 hours before going to bed. Journal of Clinical Sleep Medicine.
- EFSA Panel on Dietetic Products, Nutrition and Allergies (2015). Scientific opinion on the safety of caffeine. EFSA Journal.
- Southward, Rutherfurd-Markwick & Ali (2018). The effect of acute caffeine ingestion on endurance performance. Sports Medicine.
Related explainers
Glossary: Caffeine, Pharmacokinetics (PK)