How Many Hours Before Bed Should I Stop Caffeine?

A cutoff of about eight hours before bedtime is a reasonable starting point for most people, and longer if you are sensitive. In one lab study, a 400 mg dose of caffeine taken even six hours before bed reduced total sleep by more than an hour.

How caffeine affects sleep

Caffeine blocks adenosine receptors, which dampens the sleepiness signal that builds during the day. Its half-life averages around five to six hours but varies widely with genetics, medications, smoking and pregnancy. That means a substantial amount can still be active many hours after the last cup.

Setting your cutoff

Work backward from your usual bedtime. A bedtime of 10:30 p.m. suggests a last caffeine around 2:30 p.m.
If you are sensitive, wake often at night or sleep lightly, try 10 to 12 hours.
Count all sources: coffee, tea, energy drinks, pre-workout, some sodas and chocolate.
Test for one to two weeks and observe changes in how long it takes you to fall asleep and how rested you feel.

Decaf still contains a small amount of caffeine, typically a few milligrams per cup.

What the research says

In a randomized crossover trial of 12 healthy adults, 400 mg of caffeine taken 0, 3 or 6 hours before bed each reduced total sleep time compared with placebo, and objective measurements showed the effect even at six hours, though participants often did not perceive it. A broader systematic review found that caffeine tends to lengthen the time to fall asleep, shorten total sleep and reduce sleep efficiency.

The study was small and used a high dose, so the effect at a single cup of coffee may be smaller. Individual response varies.

A consistent wake time and morning light can help with daytime alertness without relying on late caffeine. See the complete sleep guide and the magnesium page. For using caffeine for focus, see caffeine and L-theanine.

Frequently asked questions

Is a 2 p.m. coffee too late?

For someone who sleeps at 10 or 11 p.m., 2 p.m. is about eight hours before bed, which fits a common guideline. If you are sensitive or sleep earlier, an earlier cutoff may help.

Does caffeine affect sleep even if I can fall asleep?

Yes. In lab studies, caffeine reduced total sleep time and altered sleep stages even when participants did not report trouble falling asleep.