How long does caffeine last? Half-life explained
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Caffeine has an average half-life of about four hours in healthy adults, with a range of two to eight hours, according to the European Food Safety Authority (EFSA). That means about half the caffeine from a drink is still in your body four hours later. How long it lasts varies from person to person, depending on things like age, body weight, pregnancy, medication and liver health.
Key points
• Average half-life of caffeine: about 4 hours (range 2–8 hours) in healthy adults.
• After about 8 hours, roughly a quarter of the caffeine is still in the body (at a 4-hour half-life).
• Pregnancy, some medicines and liver health can make caffeine last longer.
• EFSA says 100 mg of caffeine close to bedtime may affect sleep in some adults.
Table of contents
- What is caffeine's half-life?
- How much caffeine is left after a few hours?
- Why it varies from person to person
- Caffeine later in the day
- FAQ
What is caffeine's half-life?
The half-life is the time it takes the body to get rid of half of the caffeine. EFSA explains that in healthy adults the average half-life is about four hours, ranging from two to eight hours (EFSA explains: caffeine).
How much caffeine is left after a few hours?
An example with a cup of instant coffee (about 100 mg, according to the NHS), at the average half-life of four hours:
| Time after drinking | Caffeine still in the body (approx.) |
|---|---|
| 0 hours | 100 mg |
| 4 hours | 50 mg |
| 8 hours | 25 mg |
| 12 hours | 12.5 mg |
Work out your own total: caffeine calculator.
Illustration only, based on a 4-hour half-life. With a half-life of 8 hours, half would still be there after 8 hours.
If you have caffeine several times a day, the amounts overlap. More on daily totals: How much caffeine is too much?
Why it varies from person to person
According to EFSA, the half-life varies widely depending on:
- age
- body weight
- pregnancy (caffeine is cleared more slowly). More: Caffeine in pregnancy: UK guidance
- medication
- liver health
Sensitivity to caffeine also varies, so the same amount can feel different for different people. More: Caffeine sensitivity
Caffeine later in the day
EFSA notes that a single dose of 100 mg (about 1.4 mg per kg of body weight) may affect sleep duration and patterns in some adults, particularly when consumed close to bedtime. With a half-life of several hours, caffeine from the afternoon can still be in your body in the evening.
To keep track, check the caffeine per serving:
| Source | Caffeine |
|---|---|
| Instant coffee, 1 cup | about 100 mg |
| Espresso, 60 ml | about 80 mg |
| Tea, 1 cup | about 75 mg |
| Energy drink, 250 ml | about 80 mg |
| Cola, 1 can | about 40 mg |
| Decaf coffee, 200 ml | about 4 mg |
| Optimal Native Morning Energy / Daily Flow / Evening Relax, 1 pouch | 200 mg / 75 mg / 0 mg |
Drinks: NHS; espresso and decaf: EUFIC. More: Caffeine in an espresso · Caffeine in decaf coffee
FAQ
How long does caffeine stay in your system?
The average half-life is about four hours in healthy adults (range 2–8 hours), so it takes several half-lives for most of it to be cleared.
How long does a cup of coffee last?
At a 4-hour half-life, about half of the caffeine is still in the body four hours later and about a quarter after eight hours.
Why does caffeine last longer for some people?
Age, body weight, pregnancy, medication and liver health all affect how fast caffeine is cleared.
What happens if you stop caffeine suddenly?
Regular users can get withdrawal symptoms such as headache. More: Caffeine withdrawal
Read next: Caffeine withdrawal · How much caffeine is too much? · Caffeine in coffee vs tea vs green tea
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