LT4 kinetics · one-compartment model
Build a repeating tablet pattern, such as one skipped day a week, and see how its average compares with a target daily dose, how much the serum level swings, and what one missed or extra tablet does.
For cliniciansEducational model, not medical advice. Change a dose only under the prescribing clinician. Parameters are population estimates; see the sources below.
Patient instruction
Day 0 is a Monday. Tap a day in the dose strip for a one-off change: missed dose, then extra tablet, then back to plan. With the strip focused, use the arrow keys and Enter.
| Schedule | Cycle | Avg mcg/day | vs target | Swing |
|---|
Each tablet is treated as a separate dose that is absorbed over a few hours and then cleared exponentially. The level at any moment is the sum of what remains from every dose taken so far. This is a one-compartment model with first-order absorption and first-order elimination.
% of target is the level divided by the steady-state average that the target dose would give if taken every day. With no residual thyroid production it does not depend on F or V, so it is the most robust way to compare schedules. The total T4 view multiplies through by F and V and is only an estimate; the free T4 view is a further fixed-fraction estimate.
Swing is the steady-state peak minus the low point, divided by the schedule’s own average. A one-off change is measured against the same schedule without the change, at the same moment: “9.4% below” means 9.4% below where the level would have been.