What changes how fast you clear caffeine?
The same cup of coffee can leave two people at very different speeds. Caffeine is broken down mostly by one liver enzyme (CYP1A2), so anything that speeds it up or slows it down changes how long caffeine stays with you.
What changes the pace most
- Genetics: the largest share of the difference between people. Some are born fast, some slow.
- Smoking: speeds caffeine clearance up.
- Birth control pills: slow it down; the half-life can rise to about 5–10 hours.
- Pregnancy: slows it markedly; about 9–11 hours, longer late in pregnancy. More in Caffeine in pregnancy.
- Some medicines and liver disease: can slow it a lot.
Age and weight
In adults age matters little; the big difference is in newborns. Weight changes how concentrated caffeine is in the blood, but not noticeably how fast the total amount in your body halves. That is why Caffeine Tracker doesn’t ask your age or weight.
In Caffeine Tracker
Tap How fast I clear it on the home screen and pick Fast (≈ 3 hours), Average (≈ 5) or Slow (≈ 8). If you’re not sure, leave it on Average. The choice moves every estimate at once.
Sources: Frontiers in Pharmacology 2021 – systematic review · EFSA – caffeine opinion (slides) · National Academies – caffeine workshop
See what's still in you now →General information with sources, not medical advice.