Caffeine Before Sleep: How Many Hours Do You Need?

By Timothy Spinks

The first of October was International Coffee Day, and I am not here to spoil it. Coffee is one of the day's small pleasures and I have no wish to talk anyone out of theirs. But the same week brought round a familiar piece of advice about caffeine before sleep, and how many hours you ought to leave between your last cup and your bed, and it seemed a good moment to look at what the research says.

The short answer is this. For an ordinary cup of coffee, the cautious figure is about nine hours before bed, which for a 10pm bedtime means a last cup at around lunchtime. A single small cup later in the afternoon may be fine for many people, because the amount matters as much as the hour, and people differ a good deal in how long caffeine stays with them.

That is the number. What interests me more is what it does to the shape of a day, so let me take it a step at a time.

Caffeine before sleep: how many hours is enough?

The nine hour figure comes from one study, which pulled together the results of 24 others. Across them, caffeine cut total sleep by about 45 minutes, added around nine minutes to the time it took to fall asleep and trimmed deep sleep by about 11 minutes. From that, the researchers worked out that a cup of coffee, at roughly 107 mg of caffeine, should be drunk at least 8.8 hours before bedtime if it is not to eat into the night.

If you go to bed at 10pm, that puts the last cup at about ten past one. If you are an 11pm person, call it just after two. It is earlier than most of us would guess, and it is worth saying that this is older research being talked about again, not a new finding.

A coffee cup resting on a saucer in warm, dim light

Photo by Peter Herrmann on Unsplash

Does one afternoon coffee affect sleep?

Not always, and this is where it gets more forgiving. Another study gave a group of people either 100 mg of caffeine, which is about one cup of coffee, or 400 mg, and did so 12, 8 and 4 hours before bed. The small dose made no significant difference to sleep, even four hours before bedtime. The large dose disturbed sleep at every timing, including the one taken 12 hours earlier, and did the most harm four hours before bed.

It was a small study, 23 young men, so I would hold it loosely. Still, taken with the first one, it tells a sensible story. One modest coffee after lunch is a different thing from the third large one of the day, and the total you have drunk by mid afternoon seems to count for as much as the time on the clock.

Why does caffeine stay with you for so long?

Caffeine works by blocking adenosine, a chemical that builds up in the brain through the day and makes us feel sleepy. The tiredness is still there. We just stop feeling it for a while.

How long that lasts is very much a personal matter. One report on the research puts caffeine's half-life, the time it takes the body to clear half of it, at anywhere from 1.5 to 9.5 hours, with genes, age and the way we live all playing a part. That wide range explains the friend who has an espresso after dinner and sleeps soundly, and the rest of us who lie there at midnight, tired and oddly wired, wondering what we did wrong.

What about tea and other drinks?

Tea is gentler. The first study found no clear cut-off time for a cup of black tea, at about 47 mg of caffeine. It is worth knowing where else caffeine turns up, though. As the NHS puts it, "Tea, coffee and some soft drinks contain caffeine", so a cola with dinner belongs in the same sum.

How to move your last coffee without missing it

I do not think this needs to be a rule. I find it more useful to see it as a handover. The day has a coffee half and a calm half, and the evening we end up with is partly decided at lunchtime. Here is how I would go about it.

1. Work back from your bedtime

Take the time you would like to be asleep and count back eight or nine hours. That is your last full coffee. Treat it as a starting point and see how you feel after a week or two.

2. Make the last cup a good one

If it is the final coffee of the day, give it some care. Sit down with it. A cup you enjoy properly is easier to stop at than one you drink without noticing.

3. Step down, not off

If the afternoon feels bare without something warm, tea is a softer landing than another coffee, and decaf or a herbal tea softer still. Nobody needs to give up the habit of putting the kettle on.

4. Count the sneaky caffeine

Tea and fizzy drinks add up. It is the day's total that seems to matter, so it helps to notice what else is in the mix after lunch.

5. Give the evening its own drink

This is the part I care about most. When the coffee stops, the evening still wants something in the hand, and that drink can mark the start of winding down. The NHS suggests a warm milky drink or herbal tea. Lights low, phone away, something to read. If you want more ideas for that stretch of the night, I have written about improving your nighttime routine and how to get an early night.

A lit candle and a book resting on a chair in a dim room

Photo by Aspen Metzger on Unsplash

What to drink in the evening instead of coffee?

Anything without caffeine that you look forward to. That last part matters more than it sounds, because a drink you enjoy is what turns a cut-off time into a small pleasure and not a loss.

This is where Sleep Toniq sits for me. It is a caffeine free, alcohol free evening drink made with chamomile, honey, apple cider vinegar and orange, and it promotes rest and relaxation. You can have it chilled from the fridge or warmed through, as part of your wind-down. I think of it as the other end of the day from the morning coffee: one drink to begin, one to close. And if evenings handled this way leave you curious about the morning after, there is more in how to wake up feeling refreshed.

So enjoy your coffee, and perhaps enjoy it a little earlier. If you would like something for the calm half of the day, you can try Sleep Toniq here.