When should you stop drinking coffee before bed?

Falling asleep isn't the same as sleeping well

The people most certain that coffee doesn't affect their sleep are often the ones who drop off in minutes and wake up feeling like they never went under. Both things are true at once, which is what makes it so easy to miss.

Caffeine works by blocking adenosine — the substance that builds up all day and eventually makes you want to lie down. Block it and the tiredness doesn't go anywhere; it just stops reaching you. You can fall asleep on top of it without trouble. What thins out is the deep part of the night, and you don't notice that missing until morning.

It leaves in halves, not all at once

Caffeine doesn't wear off at a moment you could point to. It halves roughly every five hours. Follow one 100 mg cup taken at eight in the morning:

• 8:00 — 100 mg
• 13:00 — 50 mg
• 18:00 — 25 mg
• 23:00 — around 12 mg

By bedtime there's almost nothing left. Now move that same cup to four in the afternoon: 50 mg still working at nine, 25 mg at two in the morning. Same coffee, completely different night. A cup of SmartyCoffee is exactly that — 100 mg every time — so the same sums apply, with no guessing how strong the coffee came out.

Why your friend can drink espresso at ten and sleep fine

Because five hours is an average, not a rule. It runs from about three to seven depending on the person, and a few things move it:

• Smoking clears caffeine roughly twice as fast.
• Pregnancy and some contraceptive pills slow it down considerably.
• Genetics — people simply differ in how quickly they break it down.
• Liver conditions slow it down too.

So the useful test isn't a number on a page. It's whether you wake up rested. If evening coffee has genuinely never bothered you, you're probably a fast one. If one mid-afternoon cup ruins the night, you're not — and no amount of being used to it changes that.

A cut-off you can actually keep

Take your bedtime and subtract eight hours. In bed at eleven means the last cup at three. It sounds strict until you try it, and then the thing most people notice first isn't better sleep — it's that the afternoon slump they were treating with coffee was partly caused by the coffee.

If you drink coffee to concentrate rather than out of habit, that dip usually answers better to daylight and ten minutes of walking than to another cup.

This is general information, not medical advice.