How much caffeine is too much? Limits, timing and sources

For most healthy adults, up to 400 mg of caffeine a day is not linked with health concerns, according to both EFSA and the FDA. That is roughly three or four mugs of filter coffee, or about five mugs of tea. During pregnancy the NHS and EFSA advise no more than 200 mg a day. Timing matters as much as the total: caffeine can stay in your system for many hours, so an afternoon coffee can still affect your sleep at night.

The recommended limits

These are not targets, and people vary widely in how they react to caffeine. Some feel jittery after one cup; others sleep fine after an evening espresso. Genes, body size, pregnancy, some medicines and smoking all change how quickly caffeine is cleared.

How much caffeine is in common drinks

These are typical figures. The NHS gives the first six; the rest are approximate values based on USDA food data. Real amounts vary a lot with the bean or leaf, brewing method and cup size.

Coffee shop drinks can be much stronger than the home figures, because large sizes often contain two or more espresso shots. Many high-street chains publish caffeine content for their drinks. Matcha varies a lot with how much powder you use; our comparison of matcha and coffee goes into why it can feel different.

Signs you are having too much

Too much caffeine can cause:

• Feeling restless, jittery or anxious
• A fast or pounding heartbeat
• Trouble falling asleep, or lighter, broken sleep
• Headaches
• An upset stomach or needing the toilet more often

If you regularly have a lot and then stop suddenly, you may get withdrawal symptoms such as headaches, tiredness and low mood for a few days. Cutting down gradually over a week or two avoids most of this.

Caffeine and sleep

Research suggests caffeine has an average half-life of around five hours in healthy adults, meaning half of it is still in your body that long after your drink. For some people it is much longer. Studies have found that caffeine taken six hours before bed can still reduce sleep, even when people do not notice it.

A practical rule for many people is to have the last caffeinated drink by early afternoon. If you sleep badly, try an earlier cut-off for a week and see if it helps. Our evening wind-down routine covers the rest of the evening.

Hidden sources of caffeine

• Energy drinks, which can contain large amounts per can. In the UK and EU, drinks with more than 150 mg per litre must carry a high-caffeine warning stating they are not recommended for children or pregnant or breastfeeding women.
• Pre-workout powders and some sports gels, which can contain as much as several cups of coffee.
• Some cold and flu remedies and painkillers, which add caffeine. Check the leaflet.
• Chocolate and cocoa, small amounts, more in darker chocolate.
• Some soft drinks and iced teas.

Caffeine pills and pure caffeine powders are a particular risk, because it is easy to take a dangerous dose by mistake. The FDA has warned against highly concentrated and pure caffeine products sold in bulk.

Questions people ask

Is coffee bad for you?

For most healthy adults, moderate coffee drinking appears to be safe, and research has linked it with some possible benefits. The concerns are mostly about large amounts, sleep, pregnancy and sugary additions rather than coffee itself.

Does caffeine dehydrate you?

Caffeine has a mild effect on how much you need to urinate, but the water in tea and coffee more than makes up for it in people who drink them regularly. The NHS counts them towards your daily fluids.

Is caffeine safe for teenagers?

EFSA suggests about 3 mg per kg of body weight a day for children and teenagers, which is much lower than the adult limit. Energy drinks carry warnings that they are not recommended for children.

Photograph: AI-generated image

Filed under caffeine, coffee, tea, sleep.