Caffeine and sleep - how many hours before sleep should you drink your last coffee

Caffeine can interfere with sleep even when falling asleep feels normal. Many people notice an effect when coffee was consumed within about six hours of bedtime, but the range varies.

Caffeine blocks adenosine receptors in the brain. A common pattern is falling asleep on time but having lighter sleep. The half life of caffeine is about 5 to 6 hours for most people, which means a significant portion remains hours after a cup.

Some people still feel the effect 10 to 12 hours later, while others clear it sooner. The dose matters as well. One cup six hours before sleep is not the same as a double espresso at the same time.

Because sensitivity varies, the same timing can feel fine for one person and disruptive for another. This is one reason why sleep quality can feel different even when bedtime looks the same.

Trackers sometimes reflect this in numbers, but the subjective feeling in the morning often tells more about the night.