When should you stop drinking caffeine before bed?
By the Caffeine Clock team · Updated September 2026
Early enough that little caffeine is left at bedtime: the European Food Safety Authority notes that 100 mg close to bedtime can affect sleep in some adults. In a sleep study, 400 mg taken 6 hours before bed still cut sleep by more than an hour, so bigger doses need an earlier cutoff.
At bedtime (22:00)
0 mg
Below 100 mg at
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What the research says
The clearest study of timing gave people 400 mg of caffeine, the whole daily amount the FDA cites for healthy adults, either at bedtime, 3 hours before or 6 hours before, and compared each with a placebo. All three disrupted sleep. Even at 6 hours, the authors report that caffeine reduced sleep by more than an hour, and they recommend avoiding substantial caffeine for at least 6 hours before bed.
Smaller amounts matter too. The European Food Safety Authority notes that a single 100 mg dose may affect sleep duration and patterns in some adults, particularly close to bedtime. Published advice on when to stop ranges from 4 to 11 hours before bed, largely because people clear caffeine at very different speeds.
How much is left at bedtime
What reaches your bed is the amount still in your body. The table shows how much of a 200 mg drink, sipped over 10 minutes, is left at 10 pm depending on when you have it and how fast you clear caffeine.
| Drink at | 3-hour half-life | 5-hour half-life | 6-hour half-life |
|---|---|---|---|
| 8 am | 9 | 30 | 42 |
| 10 am | 14 | 40 | 52 |
| Noon | 22 | 53 | 66 |
| 2 pm | 35 | 70 | 83 |
| 4 pm | 55 | 92 | 105 |
| 6 pm | 88 | 122 | 132 |
| 8 pm | 138 | 160 | 166 |
With a 5-hour half-life, a 4 pm drink of this size is just under the 100 mg line by bedtime and a 6 pm one is over it. With a 6-hour half-life, 4 pm is already over. The 400 mg from the study, taken 6 hours before a 10 pm bedtime, would still leave about 180 mg at a 5-hour half-life.
Finding your own cutoff
Set your bedtime and half-life under Change in the calculator above, then add what you usually drink. The "At bedtime" tile shows what will be left when you go to bed, and "Below 100 mg at" shows when you drop under your sleep threshold. Moving your last drink earlier until that time lands before bedtime gives you your own cutoff.
The 100 mg default is a starting point. If you sleep badly at lower levels, lower the threshold under Change; the chart's green line moves with it. For how long a single cup stays with you, see how long caffeine lasts.
Frequently asked questions
More about caffeine
- How long does caffeine last?
- What is the half-life of caffeine?
- How much caffeine is safe during pregnancy?
- Caffeine calculator
- How the calculator works
Sources
- Drake C, Roehrs T, Shambroom J, Roth T. Caffeine effects on sleep taken 0, 3, or 6 hours before going to bed. Journal of Clinical Sleep Medicine. 2013;9(11):1195-1200. https://doi.org/10.5664/jcsm.3170
- European Food Safety Authority. Caffeine (topic page summarising the 2015 Scientific Opinion on the safety of caffeine). https://www.efsa.europa.eu/en/topics/topic/caffeine
- U.S. Food and Drug Administration. Spilling the Beans: How Much Caffeine Is Too Much? https://www.fda.gov/consumers/consumer-updates/spilling-beans-how-much-caffeine-too-much
- Mort JR, Kruse HR. Timing of blood pressure measurement related to caffeine consumption. Annals of Pharmacotherapy. 2008;42(1):105-110. https://doi.org/10.1345/aph.1k337