Splitting a weekly dose is easy arithmetic — the real question is whether it changes anything. This models the levels for both schedules and shows how much your peak drops, your trough rises, and your week-to-week swing narrows.
Enter a weekly dose and pick your days to compare schedules.
| Schedule | Peak | Trough | Swing |
|---|
None of this is medical advice, and split dosing has not been clinically studied. These compounds were trialed, approved and labeled as once-weekly injections. Splitting a weekly dose across two or more injections is something people do on their own initiative, not a regimen with trial evidence behind it.
The reasoning people give is twofold. First, side effects — nausea, reflux and other GI effects are commonly reported as worst in the day or two after an injection, and the anecdotal claim is that a smaller amount at a time is easier to tolerate. Second, more even coverage — a single weekly injection produces a peak shortly after dosing and a trough before the next one, and some people report appetite effects fading late in the week.
Both of those are claims about experience. What this tool can actually show you is the arithmetic underneath them: how much a given split changes the modeled peak, trough and swing. Whether a smaller peak translates into fewer side effects for any particular person is not something a calculator can answer — and in some cases the model will show the change is small enough that it is reasonable to question whether the extra injections are worth it.
Talk to a licensed healthcare provider before changing anything about a protocol.
Levels are modeled with single-compartment first-order elimination — the standard textbook decay model — and summed across repeating doses until they settle at steady state. Results are shown as an index with the once-weekly peak set to 100, because volume of distribution isn't modeled: the ratios between schedules are meaningful, the absolute numbers aren't.
It also assumes the full dose enters circulation immediately. Real absorption takes time, which blunts peaks further — so the true difference between schedules is usually a little smaller than modeled here. Individual variation, bioavailability and tolerance are not modeled at all.
Half-life values: semaglutide ~1 week and tirzepatide ~5 days per manufacturer labeling; retatrutide ~6 days from published phase-2 pharmacokinetic data, which is less established than the other two. Where a figure matters to you, enter your own via the custom option.
