Sleep
How late is too late for coffee?
Caffeine stays in your system far longer than it feels. How to set a cut-off from your own bedtime and sensitivity, and test it in two weeks.
Short read1h Protocols · September 28, 2026 · 2 min read
"Coffee doesn't affect me" is usually half true.
Plenty of people can drink an espresso after dinner and fall asleep. The catch is that falling asleep isn't the test. You can sleep through the night and still lose 15 to 30% of your deep sleep without noticing. You wake up unrefreshed and reach for more coffee.
Half-life and quarter-life
Caffeine works by blocking adenosine, the chemical that builds sleep pressure through the day. Its half-life is about 5 to 6 hours: that's how long your body takes to clear half of it. Its quarter-life is 10 to 12 hours. So a coffee at 2 pm still leaves roughly a quarter of its caffeine in your system around midnight.
People also differ. How fast you clear caffeine depends partly on your genes, which is why the right cut-off depends on you, not on a universal rule.
A cut-off based on your bedtime
Count back from lights-out by how sensitive you are:
| If you are… | Stop caffeine | Bed at 11 pm means |
|---|---|---|
| Not very sensitive | 8 h before bed | last coffee by 3 pm |
| Average or not sure | 10 h before bed | last coffee by 1 pm |
| Sensitive | 12 h before bed | last coffee by 11 am |
In our sleep program, your cut-off is calculated from your own lights-out time and sensitivity. If you drink coffee later than that now, the protocol moves it earlier by an hour a week rather than all at once.
Sources: Huberman Lab Guest Series with Matthew Walker, Ep 2; The Diary of a CEO E228 with Matthew Walker. Education, not medical advice.
