Estimate remaining caffeine in your system based on the standard 5-hour half-life
Assumes single-dose first-order elimination with a 5 h half-life. Real half-life ranges roughly 3-7 h and is longer in pregnancy, liver disease and with oral contraceptives, and shorter in smokers. Status labels are illustrative, not medical thresholds. Health authorities suggest up to about 400 mg/day for most healthy adults (200 mg/day in pregnancy).
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Caffeine Half Life is built on published formulas and reference ranges from established health sources. We revisit it periodically as guidance evolves; the "Last reviewed" date above shows when that last happened. If something looks wrong, tell us with the feedback button in the bottom-right corner.