This page is intended to be modified only by Philip Neff. If you are not Philip Neff, don't touch anything. I don't feel like implementing security on this yet.
Current level
Tap a preset, or enter a custom amount and time.
Doses older than a few half-lives are dropped automatically since they no longer affect your level.
Total mg logged per day, last 7 days.
Caffeine decay is modeled as simple exponential decay per dose: level(t) = mg × 0.5^((t − dose_time) / half-life). Your average half-life is ~5 hours, but genetics (CYP1A2 variants), smoking, pregnancy, and liver function can shift this significantly — adjust the setting above if you know your own rate differs.
For reference — not medical advice.
Caffeine's half-life in healthy adults averages around 5 hours, but individual measurements range from roughly 1.5 to 9.5 hours — a wide spread. Most of that variation comes down to genetics: the liver enzyme CYP1A2 does nearly all of the work breaking caffeine down, and variants in the CYP1A2 gene (along with a related gene, AHR, which influences how much of the enzyme gets made) split people into roughly "fast" and "slow" metabolizer categories. That genetic baseline then gets shifted by physical and environmental factors layered on top: smoking roughly doubles CYP1A2 activity, pregnancy can stretch the half-life past 15 hours by the third trimester, oral contraceptives slow it down, liver disease slows it further, and certain medications (some antibiotics and antidepressants) inhibit the enzyme too. In short — genetics sets your starting point, and things like smoking status, pregnancy, or medications can move you significantly from there.