How long does 600 mg of caffeine last?
About 22 and a half hours. 600 mg of caffeine peaks near 548 mg 45 minutes after you take it, halves every 5.7 hours, and falls below the 40 mg sleep threshold about 22 and a half hours later.
| Peak level, 45 minutes in | 548 mg |
| Time to fall below 40 mg | 22 and a half hours |
| Left after 6 hours | 296 mg |
| Left after 12 hours | 143 mg |
| Latest hour for an 11 pm bedtime | 12:32 am the night before |
| Share of the 400 mg daily limit | 150% |
Hour by hour
| Time after the dose | If taken at 8 am | Still active | For sleep |
|---|---|---|---|
| 1 hour | 9 am | 541 mg | still working |
| 2 hours | 10 am | 482 mg | still working |
| 4 hours | 12 pm | 378 mg | still working |
| 6 hours | 2 pm | 296 mg | still working |
| 8 hours | 4 pm | 232 mg | still working |
| 10 hours | 6 pm | 182 mg | still working |
| 12 hours | 8 pm | 143 mg | still working |
| 16 hours | 12 am | 88 mg | still working |
| 24 hours | 8 am | 33 mg | clear |
What 600 mg looks like
600 mg is half as much again as the daily limit. Reaching it takes three cans of Celsius, six mugs of filter coffee, or two scoops of a strong pre-workout.
It is still far from the amounts linked to serious harm: the US Food and Drug Administration puts toxic effects such as seizures at around 1,200 mg taken quickly, which in practice means pure powders and tablets rather than drinks. But 600 mg will keep most people awake. It needs about 22 and a half hours to fall under 40 mg, so even taken at breakfast it is still working at midnight.
| Drink | One serving | To reach 600 mg |
|---|---|---|
| Filter coffee | 96 mg per 8 oz cup | 6.2 |
| Espresso | 64 mg per 1 oz shot | 9.4 |
| Black tea | 48 mg per 8 oz cup | 12.5 |
| Red Bull | 80 mg per 8.4 oz can | 7.5 |
| Coca-Cola | 32 mg per 11.2 oz can | 18.8 |
How late can you take it?
Count back 22 and a half 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 600 mg |
|---|---|
| 9 pm | the day before |
| 9:30 pm | the day before |
| 10 pm | the day before |
| 10:30 pm | 12:02 am the night before |
| 11 pm | 12:32 am the night before |
| 11:30 pm | 1:02 am the night before |
| midnight | 1:32 am the night before |
| 1 am | 2:32 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 | 16 and a half hours | 6:45 am |
| Average | 5.7 hours | 22 and a half hours | 12:32 am the night before |
| Slow | 7.9 hours | 31 hours | the day before |
Common questions
How long does 600 mg of caffeine last?
About 22 and a half hours for an average adult. 600 mg peaks near 548 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 600 mg of caffeine a lot?
Yes. 600 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 600 mg of caffeine and still sleep?
For an 11 pm bedtime the latest is 12:32 am the night before. Move it by the same amount as your own bedtime. People who clear caffeine slowly need about 31 hours, so they should stop earlier still.
How much of a 600 mg dose is left after 12 hours?
About 143 mg, for an average adult. After 6 hours about 296 mg is still active, and after 24 hours about 33 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.
