Caffeine and sleep: timing matters

Count more than coffee

Caffeine is a stimulant found in coffee, tea and other drinks, and it can be added to supplements. A late pre-workout can add to caffeine from earlier drinks. The amount in coffee varies with the beans, preparation and portion size.

If you want to understand your routine, first list the products, approximate amounts and times. Use manufacturer information where available and mark estimates clearly. A mug size alone cannot tell you its caffeine content.

Feeling awake and sleeping well are different questions

EFSA reports that caffeine can affect sleep in some adults, particularly when consumed close to bedtime. Sensitivity differs, so a friend’s experience does not establish your response.

The NHS includes avoiding caffeine late in the day among its practical sleep suggestions. Think about your actual bedtime, including changes between workdays and days off, rather than a universal clock-time rule.

What does a half-life illustration show?

A half-life model removes half of a starting amount in each equal time interval. In a purely illustrative example, a 100 mg intake with a selected five-hour half-life leaves 50 mg after five hours and 25 mg after ten. An additional intake adds its own curve.

Changing the assumed half-life changes the amounts in this illustration. A mathematical model does not measure your metabolism, establish a safe intake or predict how well you will sleep. Its numbers are estimates based on assumptions, not a personal test.

Use the idea to examine a habit

Start with awareness rather than a target number. Check which drinks or products contain caffeine, and consider whether an earlier or caffeine-free option would fit your routine. Persistent sleep difficulty deserves a conversation with a health professional.

• Check the labelled serving size.
• Include drinks and supplements in the same list.
• Treat unknown amounts as unknown.
• Treat half-life calculations as illustrations rather than personal safety limits.