Coffee After Dark, Without Wrecking Your Sleep

Fri, 15 Aug 2025 22:30:00 -0800

Given the name, we get asked about evening coffee fairly often. The answer is less about beans than about pharmacokinetics.

The half-life problem

Caffeine’s half-life in most adults is five to six hours, though the range across individuals is wide. Genetics, liver enzyme activity, hormonal contraceptives, and smoking all shift it, and the spread runs from about two hours to over nine.

Take the middle of that range. A strong cup at 9 pm still has roughly half its caffeine circulating at 3 am, and a quarter at 9 am the next morning. That’s why “I can fall asleep after coffee” and “coffee doesn’t affect my sleep” are different claims. Sleep onset is often fine; what degrades is slow-wave sleep, and you don’t perceive that directly. You just feel unaccountably flat the next day.

Decaf on Midnight Bloom Coffee

Coffee After Dark, Without Wrecking Your Sleep

The half-life problem