How long does caffeine last?
The short answer
Caffeine reaches its peak in your blood 30 to 60 minutes after you drink it. From there it fades on a curve with a half-life of about 5 hours in a typical adult. The alert feeling usually lasts about 3 to 5 hours, but the caffeine itself sticks around much longer: roughly half is still in your system after 5 hours, a quarter after 10 hours, and an eighth after 15 hours. These are population averages and vary widely from person to person.
Peak, half-life, and the long tail
"Half-life" is the time it takes for half of a dose to clear. With a 5-hour half-life, a 200 mg cold brew looks roughly like this:
| Time after drinking | Caffeine still active |
|---|---|
| Right away (peak by ~45 min) | ~200 mg |
| 5 hours later | ~100 mg |
| 10 hours later | ~50 mg |
| 15 hours later | ~25 mg |
| 20 hours later | ~12 mg |
That long tail is the part people underestimate. Want the numbers for your own drink and timing? Use the caffeine half-life calculator.
Effects vs. how long it stays in your system
These are two different things. The effects (alertness, focus, jitters) are strongest near the peak and ease over a few hours. How long caffeine stays in your system is governed by the half-life and runs much longer. You can stop feeling caffeinated while a meaningful amount is still circulating, which is exactly why a late coffee can quietly cost you sleep.
What makes caffeine last longer or shorter
- Pregnancy and nursing: caffeine can take far longer to clear, often several times longer.
- Liver and kidney health: conditions that affect metabolism can lengthen the half-life.
- Medications: some antibiotics, antidepressants, and oral contraceptives slow caffeine clearance.
- Smoking: tends to speed clearance up, shortening the half-life.
- Genetics, age, and weight: all shift how fast you process caffeine.
Because of this range (studies report half-lives from roughly 1.5 to 9.5 hours), treat any single number as a rough guide, not a measurement. If any of the above applies to you, do not rely on estimates, and talk to a doctor or pharmacist.
Caffeine and sleep
One often-cited study found that caffeine taken 6 hours before bed measurably reduced total sleep time, even when people did not feel it. The practical takeaway is to give yourself a cutoff. Our guide on when to stop drinking coffee shows how to pick one based on your bedtime and sensitivity.
Caffeine in common drinks
| Drink | Typical caffeine |
|---|---|
| Brewed coffee (8 oz) | 95 mg |
| Espresso (1 shot) | 64 mg |
| Cold brew (16 oz) | 200 mg |
| Black tea (8 oz) | 47 mg |
| Green tea (8 oz) | 28 mg |
| Energy drink (8 oz) | 80 mg |
| Cola (12 oz) | 34 mg |
See your own caffeine curve
BrewPrint logs every cup and shows how caffeine rises and fades across your day, with a personal sleep cutoff. 100% offline. No account, no data collected.
Download on the App StoreFor reference only, not medical advice. Caffeine peak and half-life per the Institute of Medicine, Pharmacology of Caffeine (NCBI); sleep effect per Drake et al., Journal of Clinical Sleep Medicine, 2013. See our Medical Disclaimer.