Caffeine and Sleep: How Long Before Bed Should You Stop?
Caffeine is the world’s favourite stimulant, and most of us use it without thinking. The trouble is that it lingers longer than we feel it, so an afternoon coffee can quietly erode that night’s sleep. Here is how to enjoy caffeine without paying for it at 2 AM.
Key takeaways
- Caffeine’s half-life is around five to six hours for many people.
- Even caffeine taken six hours before bed can reduce sleep.
- A cutoff time in early afternoon works for most people.
How caffeine blocks sleep
Caffeine blocks adenosine, a chemical that builds up during the day and makes you sleepy. Blocking it makes you feel alert, but the adenosine is still there, which is why you can crash when caffeine wears off. The average half-life is about five to six hours, so half of an afternoon coffee may still be in your system at bedtime. Sensitivity varies a lot between people.
What research found
In a 2013 study published in the Journal of Clinical Sleep Medicine, caffeine taken six hours before bedtime reduced total sleep time by more than an hour compared with placebo, even though participants did not always feel it. That is why many people sleep better when they stop caffeine earlier than they expected.
How much is in your cup?
| Drink | Approximate caffeine |
|---|---|
| Brewed coffee (240 ml) | 80–100 mg |
| Espresso (30 ml) | 60–65 mg |
| Black tea (240 ml) | 40–50 mg |
| Cola (330 ml) | 30–40 mg |
| Energy drink (250 ml) | 70–150 mg |
Amounts vary by brand and preparation. Check labels.
Setting a cutoff
A common suggestion is to stop caffeine about eight hours before bed, which means around 2 PM for a 10 PM bedtime. If you are sensitive or struggle with sleep, try noon. Switch afternoon drinks to decaf, herbal tea or water.
Cutting back without headaches
Quitting abruptly can cause headaches and fatigue for a few days. Reduce gradually by a quarter of a cup every few days. If you use coffee to survive a short night, remember that the way out is more sleep; our sleep debt guide helps.
Special cases
Pregnant women are commonly advised to keep caffeine to about 200 mg a day. Children and teenagers should limit caffeine, including energy drinks. People with anxiety or palpitations often feel better with less. See sleep and anxiety.
Frequently asked questions
How long does caffeine stay in your system?
Its half-life averages five to six hours but varies from about three to over seven. Traces can last longer.
Does decaf have caffeine?
Yes, a small amount, usually 2 to 15 mg per cup.
References and further reading: Drake et al., 2013, Journal of Clinical Sleep Medicine (caffeine and sleep six hours before bed); American College of Obstetricians and Gynecologists guidance on caffeine in pregnancy.