Caffeine and Sleep: What to Consider About Timing

Advice on caffeine and sleep usually comes as a cut-off time: nothing after noon, nothing after 2pm, nothing within six hours of bed. The official sources do not agree on a single cut-off, and there is a good reason for that. This article goes through the questions people actually ask and what the published guidance says on each.

How does caffeine interfere with sleep?

The US National Heart, Lung, and Blood Institute (NHLBI) describes a biological need for sleep that builds the longer you are awake. A compound called adenosine is linked to it: its level in the brain rises during waking hours, and the rising level signals a shift towards sleep. Caffeine can interrupt this process by blocking adenosine.

The NHLBI also lists caffeine, with artificial light, as something that can give the body false cues to stay awake.

How long before bed should I stop?

Here is what three public health bodies say:

The figures span roughly three to eight hours, and none of these pages explains why it chose its number. One likely reason for the spread is individual difference: the US Food and Drug Administration (FDA) says people vary widely both in how sensitive they are to caffeine and in how quickly they clear it from the body. A cut-off that suits one person will be too cautious for another and too generous for a third.

A reasonable reading: if you fall asleep easily, the guidance gives you no reason to change. If you do not, six hours is a sensible first test, and you can move the cut-off earlier if it makes no difference.

Does the amount matter, or only the time?

Both. The European Food Safety Authority (EFSA) concluded in its 2015 scientific opinion that a single dose of 100 mg of caffeine may affect sleep duration and patterns in some adults, particularly when taken close to bedtime. For scale, the FDA puts a typical 12 fl oz (about 355 ml) serving of regular brewed coffee at 113 to 247 mg.

On total daily intake, the FDA has cited 400 mg a day as an amount not generally associated with negative effects for most adults. EFSA reached a similar figure: up to 400 mg a day, spread through the day, raises no safety concerns for healthy adults, with pregnant women treated separately. These are statements about general safety in most healthy adults. They are not targets, and they do not mean 400 mg will leave everyone’s sleep untouched.

How much is in what I drink?

The FDA gives these typical figures for a 12 fl oz (about 355 ml) serving:

The width of those ranges is the point. Two coffees from different places can differ by a factor of two. The FDA notes that restaurants and cafes are not required to disclose caffeine content in the US and encourages people to ask.

What about decaf, chocolate and things that are not drinks?

Decaffeinated does not mean caffeine-free. The FDA says decaf coffee typically contains 2 to 15 mg per 8 fl oz cup, and that people who react strongly to caffeine may want to avoid it as well.

The NHLBI lists chocolate alongside coffee, tea and soda as a caffeine source. The FDA adds that caffeine can turn up in energy and protein bars, ice cream, chewing gum, dietary supplements and some over-the-counter medicines. In the US, caffeine added as an ingredient must appear on the label of packaged food, but caffeine naturally present in an ingredient such as chocolate is not listed separately. Our guide to reading food labels covers how ingredient lists work more generally.

Who gets different advice?

The general figures above are for healthy adults. Several groups are handled differently, and the right step for anyone in them is a conversation with their own health professional, not a number from an article.

• Pregnancy and breastfeeding. EFSA concluded that up to 200 mg a day from all sources does not raise safety concerns for the foetus. The FDA advises people who are pregnant, trying to become pregnant or breastfeeding to talk to their health care provider about whether to limit caffeine. National advice varies, so check what applies where you live.
• Medicines and health conditions. The FDA says certain conditions and some medicines can make people more sensitive to caffeine.
• Children and teenagers. The FDA reports that medical experts advise against energy drinks for children and teens.

How can I find my own cut-off?

Two weeks of your own notes is not a scientific study, but it tells you more about your body than a general rule can.

What if I want to cut down?

The FDA’s advice for daily caffeine users is to cut back gradually. It describes caffeine withdrawal as not dangerous but potentially unpleasant. Swapping the last cup of the day for decaf or a caffeine-free drink is a common first step; our article on hydration and why needs differ looks at everyday drinks more broadly.

The FDA lists a faster heartbeat, palpitations, anxiety, jitters, upset stomach, headache and insomnia among the signs of having too much caffeine, and suggests speaking to a health professional if you notice them.