Afternoon Coffee and Sleep: Why 6 Hours Before Bed May Not Be Enough

Many of us follow a “no coffee after lunch” rule, or think a 3 p.m. latte is fine if bedtime is at 10. A well-known sleep study tested what caffeine at different times does to sleep at home.

The study

Researchers gave 12 healthy adults 400 milligrams of caffeine, or a placebo, at bedtime, 3 hours before bed or 6 hours before bed, and measured sleep with a home sleep monitor.¹

• Caffeine at all three times disrupted sleep compared with placebo.¹
• Even 6 hours before bed, caffeine cut sleep by more than an hour.¹

The authors suggested avoiding substantial caffeine for at least 6 hours before bedtime and, for big doses like those in large coffee-shop drinks, stopping before 5 p.m.¹

Keep in mind it was a small study of adults aged 19 to 48 who took a large single dose.¹

How much is 400 milligrams?

The FDA² says about 400 milligrams a day, roughly two to three 12-ounce cups of coffee, isn’t generally linked to harmful effects in most adults.² In the study, that full amount came at once, which is more than many people drink in one sitting.¹²

Why your cutoff may need to be earlier

• People clear caffeine at very different speeds.¹² That’s why advice on when to stop ranges from 4 to 11 hours before bed.¹
• Some health conditions and medicines make people more sensitive to caffeine.² Ask your pharmacist about yours.
• Hidden caffeine in tea, cola, chocolate, energy drinks and some pain relievers adds up. Our guide to decaf coffee explains why decaf isn’t caffeine-free.

Too much caffeine can cause sleep problems, a racing heart, palpitations and anxiety.² It can also stir up urgency for some women. Our article on caffeine and bladder leaks covers that.

Try this

1. Track your caffeine and sleep for two weeks.
2. Move your last cup earlier by an hour or two and see what changes.
3. Swap the afternoon cup for herbal tea or water.

Our guides to alcohol and sleep and CBT for insomnia cover other common sleep disruptors.

Try: “I have two coffees before noon and a latte at 3 p.m. Could that be why I’m lying awake at 11?”

Did I Do That in My Sleep? includes a 14-Night Lights-Out Record and a Visit Brief. Use them to log caffeine timing next to how long it takes you to fall asleep. See the book.