Stories · Drinks
Caffeine: how much is fine, and when to stop for the day
What caffeine does, the daily amount regulators consider fine for most adults, and how coffee, cold brew and matcha compare.
The short answer
Caffeine makes you feel less tired by blocking adenosine, the signal that builds up sleepiness through the day. For most adults, both the US FDA and Europe's EFSA put the line at about 400 mg a day, and EFSA adds up to 200 mg in one go. During pregnancy the EFSA figure is 200 mg a day. Close to bedtime, even 100 mg can affect sleep for some people.
Numbers worth knowing
- 400 mg a day: not generally associated with negative effects for most adults (FDA), and of no safety concern for non-pregnant adults (EFSA).
- 200 mg: a single dose EFSA considers of no safety concern for healthy adults.
- 200 mg a day: EFSA's level for pregnant and breastfeeding women.
- 100 mg close to bedtime may affect sleep in some adults (EFSA).
- A 12 fl oz (355 ml) brewed coffee typically has 113 to 247 mg. The same size green tea has about 37 mg (FDA).
What it does
Through the day a molecule called adenosine builds up in your brain and makes you feel sleepy. Caffeine fits into the same receptors and blocks it. You are not getting new energy. You are muting the tired signal for a while.
How much is fine
The FDA cites 400 mg a day as an amount not generally associated with negative effects for most adults, about two to three 12 fl oz cups of coffee. EFSA reached the same daily figure and adds that single doses up to 200 mg raise no safety concern for healthy adults.
People differ a lot, both in how sensitive they are and in how fast they clear it. Jitters, a racing heart, an upset stomach or poor sleep are the signs that your own line is lower.
What is in the cup
According to the FDA, a 12 fl oz (355 ml) brewed coffee typically has 113 to 247 mg of caffeine, black tea about 71 mg and green tea about 37 mg. Matcha has 18.9 to 44.4 mg per gram of powder, so a 2 g serving lands at roughly 40 to 90 mg.
Cold brew varies widely with the recipe: how much coffee, how long it steeps, how much it is diluted. Be suspicious of any single number for it.
When to stop for the day
There is no universal cut-off, because people clear caffeine at very different speeds. EFSA notes that 100 mg close to bedtime may affect how long and how well some adults sleep.
A practical test: if you sleep badly, move your last cup earlier by a couple of hours and see what changes.
Who should take less
EFSA's level for pregnant and breastfeeding women is 200 mg a day from all sources. The FDA advises talking to your doctor if you are pregnant, breastfeeding, on medication or have a condition that makes you sensitive to caffeine, and medical experts advise against energy drinks for children and teenagers.
Quick questions
- How much caffeine is safe per day?
- About 400 mg a day for most adults. The US FDA says that amount is not generally associated with negative effects, and EFSA says it raises no safety concern for non-pregnant adults. For pregnant and breastfeeding women, EFSA's figure is 200 mg a day.
- Is cold brew stronger than regular coffee?
- It depends on the recipe. Cold brew is often made as a concentrate and then diluted, so the caffeine in the cup varies widely from one shop to another.
- How late can I drink coffee?
- There is no single cut-off. EFSA notes that 100 mg close to bedtime may affect sleep in some adults, so if you sleep badly, try having your last cup earlier.
Sources
- US FDA. Spilling the Beans: How Much Caffeine Is Too Much?
- EFSA. Caffeine (summary of the 2015 scientific opinion).
- EFSA. Scientific Opinion on the safety of caffeine. EFSA Journal, 2015.
- Kochman J, et al. Health Benefits and Chemical Composition of Matcha Green Tea: A Review. Molecules, 2021.
*This article is general information and does not replace advice from your doctor. If you are pregnant, on medication or managing a condition, ask your doctor first.
