Halflife — caffeine in your system

Halflife

0mg

in your bloodstream —

Under 50 mg

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Today's peak

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At bedtime

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Caffeine in blood Sleep window 50 mg guide Hover for values · drag a cup to move it

Half-life & sleep

Caffeine leaves the body exponentially. The half-life is how long it takes for half of it to clear; 5 h is a typical adult value, but genes, smoking, hormones and pregnancy move it a lot.

Half-life5.0 h

Bedtime8 h window shown on the chart

Sources

Where the numbers come from.

Half-life ~5 h in healthy adults, range roughly 1.5–9.5 h: Institute of Medicine, Caffeine for the Sustainment of Mental Task Performance (2001), ch. 2.
Genetic (CYP1A2), smoking, oral-contraceptive and pregnancy effects on clearance: Nehlig, Interindividual Differences in Caffeine Metabolism, Pharmacol Rev 2018.
Peak blood level 30–60 min after drinking: same IOM chapter; the model uses first-order absorption tuned to peak at ~45 min.
Diet Coke 46 mg per 12 fl oz: The Coca-Cola Company. Larger sizes scale linearly.
K-Cup ~75–150 mg per pod depending on roast and brand; 100 mg is a common midpoint, 130 mg for "extra bold" or 2X pods: Keurig and brand labels. Tap any dose's mg to override.