How the clocks work

Every substance that enters the blood is cleared over time, usually at a rate proportional to how much is there. The half-life is how long it takes for half of it to leave. One half-life after a dose, 50% is left; two, 25%; three, 12.5%; after five, under 3%, which we count as "gone".

Doses add up: if you take another dose before the last one has cleared, the clock shows more than one dose in your blood (for example "1.5× a dose").

Some things keep working after they leave the blood: acid blockers switch off acid pumps for a day, aspirin disables platelets for a week. Those get an "Effect" clock. Some things act locally and barely enter the blood at all (antacids, laxatives, gas relief); they get a simple working window instead. Vitamins and minerals build up in the body and have no daily clock.

The figures are standard adult references. Age, weight, kidney and liver function, food, genetics and other substances all change the real numbers, so treat the clocks as a sense of timing, not a measurement.