How long does caffeine stay in the body?
Half-life in adults: 4–6 hours. After 8–10 hours, most of it is metabolized. For pregnant women, up to 15 hours; for smokers, only 3 hours. Rule of thumb: last coffee 6 hours before bedtime.
How long does caffeine stay in the body?
Half-life in adults: 4–6 hours. After 8–10 hours, most of it is metabolized. For pregnant women, up to 15 hours; for smokers, only 3 hours. Rule of thumb: last coffee 6 hours before bedtime.
Why that is
Caffeine is metabolized in the liver by the enzyme CYP1A2. The speed of this breakdown varies greatly between individuals—genetics, age, medication, and lifestyle play a huge role.
Half-life by group:
| Group | Half-life |
|---|---|
| Healthy adults | 4–6 hours |
| Smokers | ~3 hours |
| Pregnant women | 9–15 hours |
| Women on birth control | 5–10 hours |
| Newborns | up to 100 hours |
| Children (1–9 years) | ~3 hours |
What “half-life” means: After 5 hours (on average), half of the caffeine is metabolized. Out of 100 mg, 50 mg remain after 5 hours, and 25 mg after 10 hours—still enough to cause problems for sensitive sleepers.
What affects metabolism speed:
- Genetics: Some people are “fast metabolizers” (CYP1A2 variant), others are “slow.” Fast metabolizers can drink coffee in the evening and still sleep. Slow metabolizers still feel that 2 PM espresso at midnight.
- Smoking: Tobacco smoke significantly speeds up caffeine breakdown. Smokers often need more coffee for the same effect.
- Pregnancy: Caffeine metabolism slows down drastically—a key reason for the 200 mg recommendation.
- Medication: Birth control pills, certain antidepressants, and antibiotics (fluoroquinolones) slow down the breakdown.
- Age: Metabolism tends to slow down after age 60.
Practical rules of thumb:
- Last coffee at least 6 hours before bedtime.
- If you want to go to bed at 10 PM: last coffee by 4 PM.
- If you have sleep problems: increase the gap to 8 hours.
In practice at Green Wall Coffee
At Sophienstraße 27, we close at 5 PM—which works out well. If you have your last coffee with us, you have enough of a gap before the evening. For sensitive guests, I recommend a decaf espresso in the afternoon—with a good roast, you can barely tell the difference.
Related questions
- Does coffee help against tiredness - or is it a myth?
- How much caffeine is in a cup of coffee?
- How many cups of coffee a day are safe?
Stop by Sophienstraße 27 — Mon–Fri 8am–5pm, Sat 10am–5pm.
Visit us in Lichtenberg!
Drop by at Sophienstraße 27 — Mon–Fri 8am–5pm, Sat 10am–5pm.
Directions & Details