How long does caffeine last?
Caffeine has an average half-life of roughly 5 hours. So after 5 hours half of the amount you consumed is still active in your body, and after 10 hours a quarter. Work out below how much caffeine is still active at your bedtime.
How long does your caffeine last?
EFSA guidance: up to 400 mg per day is considered safe for healthy adults.
Half-life 5 h — median in healthy adults.
beforehand, so that less than ~25 mg of caffeine remains (sleep-friendly).
Estimate based on average half-lives. Individual caffeine metabolism varies widely (genetics/CYP1A2, liver function, medication). Not medical advice. No inputs are stored.
What influences caffeine half-life
Genetics (CYP1A2)
Metabolism runs almost entirely through the liver enzyme CYP1A2. Its activity is genetically determined — “fast” and “slow” metabolisers respond to the same cup completely differently.
Smoking
Nicotine induces CYP1A2 and shortens the half-life to around 3 to 4 hours. After quitting, metabolism slowly returns to normal.
The pill & pregnancy
Oestrogens inhibit metabolism. In late pregnancy the half-life can rise beyond 15 hours — and caffeine acts correspondingly longer.
Time of day & sleep
Caffeine blocks adenosine receptors and so suppresses tiredness. Drinking too much in the afternoon pushes back sleep onset and shortens deep sleep, often without you noticing.
Frequently asked questions about caffeine
How long does caffeine stay in the body?→
Caffeine has an average half-life of around 5 hours. So after 5 hours half of the amount consumed is still active, and after 10 hours a quarter. The individual range runs from 1.5 to more than 9 hours, depending on genetics, smoking, pregnancy and medication.
How is caffeine half-life calculated?→
Caffeine is metabolised exponentially. From the starting amount and the half-life, the remaining amount follows the formula: remaining caffeine = starting amount × 0.5^(hours / half-life). With a half-life of 5 hours, 200 mg leaves 100 mg after 5 hours and 50 mg after 10 hours.
When should I have my last coffee?→
As a rule of thumb, take your last caffeinated dose around 6 hours before going to bed. Studies show that even 400 mg of caffeine 6 hours before bedtime can measurably shorten sleep duration. If you are sensitive or metabolise caffeine slowly, allow more time.
Why does caffeine not clear at the same rate in everyone?→
Metabolism runs predominantly through the liver enzyme CYP1A2, whose activity differs genetically. Smoking speeds it up; oestrogens (the pill, pregnancy) slow it down considerably. That is why the same cup acts hours longer in some people than in others.