How long does 150 mg of caffeine last?
About 11 hours. 150 mg of caffeine peaks near 137 mg 45 minutes after you take it, halves every 5.7 hours, and falls below the 40 mg sleep threshold about 11 hours later.
| Peak level, 45 minutes in | 137 mg |
| Time to fall below 40 mg | 11 hours |
| Left after 6 hours | 74 mg |
| Left after 12 hours | 36 mg |
| Latest hour for an 11 pm bedtime | 11:56 am |
| Share of the 400 mg daily limit | 38% |
Hour by hour
| Time after the dose | If taken at 8 am | Still active | For sleep |
|---|---|---|---|
| 1 hour | 9 am | 135 mg | still working |
| 2 hours | 10 am | 120 mg | still working |
| 4 hours | 12 pm | 94 mg | still working |
| 6 hours | 2 pm | 74 mg | still working |
| 8 hours | 4 pm | 58 mg | still working |
| 10 hours | 6 pm | 46 mg | still working |
| 12 hours | 8 pm | 36 mg | clear |
| 16 hours | 12 am | 22 mg | clear |
| 24 hours | 8 am | 8 mg | clear |
What 150 mg looks like
150 mg is a large coffee-shop filter, a can of Rockstar, or a mug of coffee followed by a cup of tea. It is an ordinary amount to have by mid-morning and an awkward one to have after lunch.
The awkward part is the tail. Caffeine leaves by halves: getting from 150 mg down to 75 takes 5.7 hours, and getting from 75 to under 40 takes almost as long again. That is why a dose only half as large again as a mug of coffee needs about 11 hours to clear.
One serving of these holds about 150 mg: Monster (160 mg), Rockstar (151 mg).
| Drink | One serving | To reach 150 mg |
|---|---|---|
| Filter coffee | 96 mg per 8 oz cup | 1.6 |
| Espresso | 64 mg per 1 oz shot | 2.3 |
| Black tea | 48 mg per 8 oz cup | 3.1 |
| Red Bull | 80 mg per 8.4 oz can | 1.9 |
| Coca-Cola | 32 mg per 11.2 oz can | 4.7 |
How late can you take it?
Count back 11 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 150 mg |
|---|---|
| 9 pm | 9:56 am |
| 9:30 pm | 10:26 am |
| 10 pm | 10:56 am |
| 10:30 pm | 11:26 am |
| 11 pm | 11:56 am |
| 11:30 pm | 12:26 pm |
| midnight | 12:56 pm |
| 1 am | 1:56 pm |
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 | 8 hours | 2:57 pm |
| Average | 5.7 hours | 11 hours | 11:56 am |
| Slow | 7.9 hours | 15 hours | 7:49 am |
Common questions
How long does 150 mg of caffeine last?
About 11 hours for an average adult. 150 mg peaks near 137 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 150 mg of caffeine a lot?
It is a moderate dose. 150 mg is within the 200 mg that the European Food Safety Authority considers safe to take at once, and 38% of the 400 mg daily limit.
How late can I take 150 mg of caffeine and still sleep?
For an 11 pm bedtime the latest is 11:56 am. Move it by the same amount as your own bedtime. People who clear caffeine slowly need about 15 hours, so they should stop earlier still.
How much of a 150 mg dose is left after 12 hours?
About 36 mg, for an average adult. After 6 hours about 74 mg is still active, and after 24 hours about 8 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.
