Guides

Plain, sourced answers about caffeine: how much is in your drink, how long it stays in your body, what research says about sleep, and what changes it.

• How much caffeine is in coffee, tea and cola?

  Roughly how much caffeine is in a cup of coffee, a glass of tea, a can of cola and other everyday drinks, why the numbers vary, and where they come from.

• How long does caffeine stay in your body?

  What caffeine's half-life means, how much of a morning coffee is still there in the evening, and why it ranges from about 2 to 8 hours between people.

• When should you stop caffeine before bed?

  Findings from two key studies on caffeine and sleep: caffeine taken six hours before bed, and the 2023 meta-analysis of 24 studies that suggests how long to leave.

• What changes how fast you clear caffeine?

  How genetics, smoking, birth control pills, pregnancy and some medicines change how fast caffeine leaves your body, and why age and weight matter less than you'd think.

• Caffeine in pregnancy: general information

  The general figure official bodies give for caffeine in pregnancy, why caffeine is cleared more slowly while pregnant, and what 200 mg looks like in everyday drinks.

General information with sources, not medical advice.