August 2026

How Long Before Bed Should You Stop Drinking Coffee?

Most people answer this with a number they picked up somewhere — 2pm, 4pm, nothing after dinner — and then judge whether it worked by whether they lay awake that night. That test is the problem. Falling asleep is only one of the things caffeine changes, and the one it changes least reliably.

Caffeine leaves your body more slowly than it feels like it does

Caffeine has a half-life of about five to six hours in most healthy adults. Half of what you drank at 2pm is still in circulation around 8pm, and a quarter of it is still there near midnight.

Through the day, a molecule called adenosine builds up in the brain, and rising adenosine is much of what makes you feel like sleeping. Caffeine blocks the receptors adenosine binds to. It does not remove your sleep pressure, it hides it. The tiredness is still accumulating; you just stop receiving the message.

That is why an afternoon coffee can matter even when you fall asleep normally. What counts is how much caffeine is still occupying those receptors while you sleep.

What the research found about a six-hour cutoff

In a 2013 study published in the Journal of Clinical Sleep Medicine, Drake and colleagues gave people 400 mg of caffeine — about four cups of brewed coffee — at three points: immediately before bed, three hours before, and six hours before.

All three disrupted sleep. The six-hour result is the one worth knowing about: a dose taken in the late afternoon still measurably interfered with sleep that night. The authors concluded that people should avoid substantial caffeine for at least six hours before bed.

“I can fall asleep fine on coffee” is probably true and beside the point

The bigger effect is on slow-wave sleep, the deepest stage, and the one most associated with feeling restored the next day.

You can fall asleep quickly, stay asleep, spend a normal eight hours in bed, and still wake up feeling like you did not rest. If your complaint is next-day fogginess rather than lying awake at night, an afternoon coffee is worth ruling out even if you are confident it does not keep you up.

A practical cutoff

Work backwards from when you want to be asleep, not from a fixed clock time. Eight hours ahead of your target bedtime is conservative and will suit slow metabolizers. Six hours is a reasonable default. If you go to bed at 11pm, that puts your last coffee between 3pm and 5pm.

Then adjust, because the variation between people is large. A gene called CYP1A2 governs much of how fast you clear caffeine, and fast and slow metabolizers can differ severalfold. This is why one person’s 4pm espresso is genuinely fine and another’s ruins the night. Keep your cutoff consistent for a week or two before judging it, and pay attention to how you feel the following afternoon, not just how quickly you fell asleep.

“I’ll switch to decaf” — the part people miss

Decaf is not caffeine-free. Decaffeination removes most of the caffeine, not all of it, and how much survives varies between beans, brands and brewing method. A large decaf, or a few over an evening, adds up to more than people assume.

For most people this is a small amount and will not matter. For a slow metabolizer, or someone drinking several cups late, it can be enough to notice. Rest has a breakdown of how much caffeine is typically left in decaf and what that means for sleep.

If the sleep problem outlasts the coffee change

Sometimes caffeine timing was the whole issue and fixing it fixes the sleep. Often it is not.

If you have moved your cutoff earlier for a few weeks and sleep still is not recovering, the things worth looking at next are behavioral rather than chemical. Getting up at the same time every day, weekends included, does more for most people than changing bedtime. Getting out of bed when you have been awake a while, instead of lying there, stops your brain learning that bed is a place for being awake. Morning daylight helps anchor the whole rhythm.

None of that is dramatic and all of it is slow. Structured programs built on those principles exist. Readers interested in learning more can explore CBT-I resources at Rest.

If sleeplessness has gone on for months, or you suspect something like sleep apnea, that is a conversation with a doctor rather than a scheduling problem.

Six to eight hours before bed is a sensible default, and worth keeping steady long enough to judge properly. Count your decaf while you are at it. And if you sleep badly and drink coffee to cope, check whether the two are connected before you assume they are not.