How long does 500 mg of caffeine last?
About 21 hours. 500 mg of caffeine peaks near 456 mg 45 minutes after you take it, halves every 5.7 hours, and falls below the 40 mg sleep threshold about 21 hours later.
| Peak level, 45 minutes in | 456 mg |
| Time to fall below 40 mg | 21 hours |
| Left after 6 hours | 247 mg |
| Left after 12 hours | 119 mg |
| Latest hour for an 11 pm bedtime | 2:02 am the night before |
| Share of the 400 mg daily limit | 125% |
Hour by hour
| Time after the dose | If taken at 8 am | Still active | For sleep |
|---|---|---|---|
| 1 hour | 9 am | 450 mg | still working |
| 2 hours | 10 am | 402 mg | still working |
| 4 hours | 12 pm | 315 mg | still working |
| 6 hours | 2 pm | 247 mg | still working |
| 8 hours | 4 pm | 194 mg | still working |
| 10 hours | 6 pm | 152 mg | still working |
| 12 hours | 8 pm | 119 mg | still working |
| 16 hours | 12 am | 73 mg | still working |
| 24 hours | 8 am | 28 mg | clear |
What 500 mg looks like
500 mg is over the 400 mg daily limit for a healthy adult. It is rarely one drink. It is usually a day that got away: two strong coffees, an energy drink and a pre-workout.
At this level the common complaints are a fast pulse, shaky hands, an unsettled stomach and a night of light, broken sleep. For most healthy adults that is unpleasant rather than dangerous, but it is the body saying the dose is too high. If your days regularly add up to this, cut the last drink first: it is the one still active at bedtime.
| Drink | One serving | To reach 500 mg |
|---|---|---|
| Filter coffee | 96 mg per 8 oz cup | 5.2 |
| Espresso | 64 mg per 1 oz shot | 7.8 |
| Black tea | 48 mg per 8 oz cup | 10.4 |
| Red Bull | 80 mg per 8.4 oz can | 6.2 |
| Coca-Cola | 32 mg per 11.2 oz can | 15.6 |
How late can you take it?
Count back 21 hours from the time you go to bed. Each bedtime below has its own page with the cutoff for every drink.
| Bedtime | Latest hour for 500 mg |
|---|---|
| 9 pm | 12:02 am the night before |
| 9:30 pm | 12:32 am the night before |
| 10 pm | 1:02 am the night before |
| 10:30 pm | 1:32 am the night before |
| 11 pm | 2:02 am the night before |
| 11:30 pm | 2:32 am the night before |
| midnight | 3:02 am the night before |
| 1 am | 4:02 am the night before |
If you clear caffeine faster or slower
Half-life runs from about four hours in fast metabolisers to eight or more in slow ones, and the difference compounds over a day.
| Metabolism | Half-life | Clears in | Latest for 11 pm |
|---|---|---|---|
| Fast | 4.1 hours | 15 hours | 7:49 am |
| Average | 5.7 hours | 21 hours | 2:02 am the night before |
| Slow | 7.9 hours | 29 hours | the day before |
Common questions
How long does 500 mg of caffeine last?
About 21 hours for an average adult. 500 mg peaks near 456 mg active 45 minutes after you take it, then halves every 5.7 hours until it falls below 40 mg, the line Cira uses as low enough to sleep on.
Is 500 mg of caffeine a lot?
Yes. 500 mg is above the 400 mg daily limit for a healthy adult, the figure used by the European Food Safety Authority and the US FDA.
How late can I take 500 mg of caffeine and still sleep?
For an 11 pm bedtime the latest is 2:02 am the night before. Move it by the same amount as your own bedtime. People who clear caffeine slowly need about 29 hours, so they should stop earlier still.
How much of a 500 mg dose is left after 12 hours?
About 119 mg, for an average adult. After 6 hours about 247 mg is still active, and after 24 hours about 28 mg.
Other doses
Look it up another way
Where these numbers come from
Every figure is calculated with the model the Cira app uses: caffeine peaks 45 minutes after you take it and halves every 5.7 hours, a typical value for healthy adults. The 40 mg sleep line is a working threshold of the model, and the 400 mg daily limit is the figure used by the European Food Safety Authority and the US FDA. These are averages. Smoking, pregnancy, the contraceptive pill and some medicines change how fast you clear caffeine. How the numbers are worked out.
