Different molecules, different rules. The one that trips people up: the missed-dose window is a full day shorter on tirzepatide. Apply the wrong one and you either inject too late or skip a dose you didn't need to.
Semaglutide's missed-dose window is 5 days. Tirzepatide's is 4 days. The gap tracks their half-lives — roughly 7 days for semaglutide versus 5 for tirzepatide — but the practical effect is simple: a rule that's safe on one drug is a day too late on the other.
Sources: Ozempic/Wegovy (semaglutide) and Mounjaro/Zepbound (tirzepatide) prescribing information, Novo Nordisk and Eli Lilly. Aronne et al., JAMA 2025 (SURMOUNT-5 head-to-head trial). Not medical advice — confirm your specific medication's rules with your prescriber.
*SURMOUNT-5 (Aronne et al., JAMA 2025) · individual response varies · not medical advice
Head-to-head data favors tirzepatide for average weight loss, but "more effective on average" isn't the same as "better for you." Semaglutide has a longer real-world track record, a slightly wider missed-dose window, and is often easier to access depending on insurance formularies. Tirzepatide's dual mechanism tends to produce a stronger response for many patients, at the cost of a narrower margin if a dose slips.
Neither drug changes where you inject — both use the same three approved sites and the same rotation logic. What changes is the clock on a missed dose, and that's the rule people most often get wrong when they've been on one medication and switch to, or hear advice meant for, the other.
The app doesn't apply one generic "missed dose" rule — it stores your exact medication and enforces its real window.
Move from semaglutide to tirzepatide, or the reverse, and the rules update automatically with you.
Same abdomen/thigh/arm rotation logic for both — the app remembers your last site regardless of medication.
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