Caffeine & Your Body
Half-life, sleep, tolerance, and the crash — how caffeine moves through you and how to time it.
Caffeine has a half-life of about five to six hours in most adults, which means a 2 p.m. coffee can still leave a quarter of its caffeine in your system at bedtime. That’s why timing matters as much as dose when it comes to sleep.
These guides explain how your body metabolizes caffeine, why tolerance builds, what causes the afternoon crash, and how to use a caffeine cutoff time. Our Caffeine Half-Life Calculator plots exactly how much is left in your system hour by hour.
3 articles in “Caffeine & Your Body”
How Long Does Caffeine Last in Your System?
Caffeine peaks 30–60 minutes after you drink it and has a half-life of about 5 hours, so a quarter of your coffee is still working 10 hours later. Here is the full timeline and what changes it.
When to Stop Drinking Coffee Before Bed
To protect your sleep, stop drinking coffee about 8–10 hours before bed — research shows caffeine 6 hours before bedtime still disrupts sleep. Here is how to find your personal cutoff.
How Much Caffeine Is Too Much? The Safe Daily Limit
The FDA considers up to 400 mg of caffeine a day — about four cups of coffee — safe for most healthy adults. Here is what that means in cups, the signs of too much, and who should have less.
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