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Steady state, explained: why week 5 on a GLP-1 feels different from week 1
Steady state is the point where the medication entering your body each week equals the amount leaving it, so your levels settle into a stable weekly rhythm. With half-lives of ~5–7 days, semaglutide and tirzepatide reach steady state after roughly 4–5 weeks at the same dose. Until then, your level climbs every week — which is why early weeks keep changing.
What does “steady state” actually mean?
Every dose you inject doesn’t vanish before the next one — with a half-life of about 7 days for semaglutide (Ozempic, Wegovy) and ~5 days for tirzepatide (Mounjaro, Zepbound), roughly half of last week’s dose is still working when the next one lands. Each week’s injection stacks on the remainder of the previous ones, so your average level climbs.
That climb can’t continue forever: the more medication in your body, the more gets eliminated each day. Steady state is the equilibrium — intake equals elimination, and your weekly curve stops climbing and starts repeating.
Why does shot day feel different from day six?
Even at steady state, your level isn’t flat — it’s a sawtooth. It peaks 1–3 days after the injection, then drifts down to a trough right before the next dose. Semaglutide’s weekly peak-to-trough swing is relatively gentle; tirzepatide’s shorter half-life makes its trough comparatively deeper.
Many people can feel the sawtooth: appetite suppression that’s strongest mid-week, an appetite return the day before their shot, or side effects that cluster after injection day. None of this is imagined — it’s the curve.
Why do the first weeks keep changing?
Two things move at once early on. First, accumulation: at the same dose, week 2’s average level is meaningfully higher than week 1’s. Second, titration: labeled schedules step the dose up every 4 weeks, and every step restarts the climb toward a new, higher steady state.
This is why clinicians say “give it time” — your body isn’t experiencing the final treatment in week one. It’s experiencing a fraction of it that grows every week.
How long until steady state on each medication?
| Medication | Half-life | Steady state at a fixed dose |
|---|---|---|
| Semaglutide (Ozempic, Wegovy, Rybelsus) | ≈ 1 week | ≈ 4–5 weeks |
| Tirzepatide (Mounjaro, Zepbound) | ≈ 5 days | ≈ 4 weeks |
| Dulaglutide (Trulicity) | ≈ 4.7 days | 2–4 weeks |
| Liraglutide (Saxenda, Victoza) | ≈ 13 hours | ≈ 3 days |
Remember the asterisk: each dose increase resets the clock. If you titrate every 4 weeks, you’re essentially always approaching a new steady state until you reach your maintenance dose.
Does steady state mean results plateau?
No — it means your medication level stabilized, not your progress. Appetite effects, weight change and side-effect patterns keep evolving for months after levels steady. But knowing your level has stabilized is useful context: if something changes at week 8 at a fixed dose, the cause probably isn’t “more drug”.
Sources
- FDA Prescribing Information — Ozempic (semaglutide): Clinical Pharmacology — half-life ≈ 1 week; steady state 4–5 weeks
- FDA Prescribing Information — Mounjaro/Zepbound (tirzepatide): Clinical Pharmacology — half-life ≈ 5 days; steady state ≈ 4 weeks
- Rowland & Tozer, Clinical Pharmacokinetics and Pharmacodynamics — accumulation and the 4–5 half-life rule
This article is educational and is not medical advice, diagnosis or treatment. Medication decisions — including dose changes and what to do after a missed dose — belong with your prescriber. If you experience severe symptoms, seek medical care.