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How much caffeine is still in you at bedtime?
Half of an afternoon coffee is usually still in your blood five hours later. Add what you drink in a day and when, and see your total and what is left when you go to bed.
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Up to 400 mg a day; half-life about 5 hours (2 to 10 in different people).
then tap what you had.
Coffee
Tea
Soft and energy drinks
Chocolate, tablets and powders
Wondering whether coffee is behind your palpitations or poor sleep?
Dr. Triveni can look at a normal week of what you eat and drink and help you find what to change.
Book a consultationWhere the numbers come from
Limits: the European Food Safety Authority, the US FDA and Health Canada put up to 400 mg a day as safe for healthy adults, with single doses up to 200 mg. In pregnancy the advice is no more than 200 mg a day (EFSA, NHS, the American College of Obstetricians and Gynecologists). Children and teenagers: about 3 mg per kg of body weight a day at most.
Half-life: about five hours in an average adult, with a range of roughly two to ten. It roughly doubles on the combined pill, lengthens through pregnancy to around 10 to 15 hours by the third trimester, and is shorter in smokers (about three hours). The curve assumes each drink is absorbed straight away; in reality caffeine peaks 30 to 60 minutes after drinking, so the real curve is a little later and smoother. Caffeine per serving is typical, from USDA FoodData Central and chain nutrition tables; cafe sizes and brewing vary a lot.
What the trials found on palpitations, atrial fibrillation, blood pressure and sleep: Coffee and your heart.
General information, not medical advice. If you have palpitations, chest pain, a heart rhythm problem, high blood pressure or anxiety, or take medicines that interact with caffeine, ask your doctor what is right for you.