Tirzepatide vs Semaglutide: A Head-to-Head Comparison

Tirzepatide and semaglutide are the two most widely used incretin medicines, and unlike many drug comparisons, these two have actually been studied head-to-head. Both are FDA-approved and given as once-weekly injections. Tirzepatide is sold as Mounjaro (diabetes) and Zepbound (weight management); semaglutide is sold as Ozempic (diabetes), Wegovy (weight management), and Rybelsus (oral, diabetes). Here's how they compare.

Important: This page is educational and not medical advice. Only a healthcare provider can determine which medicine, if any, is appropriate for you.

What is the difference between tirzepatide and semaglutide?

The core difference is mechanism. Semaglutide is a single-receptor GLP-1 agonist. Tirzepatide is a dual agonist that activates both the GLP-1 and GIP receptors. That extra GIP activity is thought to contribute to tirzepatide's larger average weight loss in the trials done so far.

Side-by-side comparison

The head-to-head trial: SURMOUNT-5

Unusually for two competing drugs, tirzepatide and semaglutide were compared directly in the SURMOUNT-5 trial (published in the New England Journal of Medicine in 2025). Over 72 weeks, tirzepatide produced about 20.2% average weight loss versus about 13.7% with semaglutide, roughly 50 lb versus 33 lb. About 32% of tirzepatide participants lost at least 25% of their body weight, compared with about 16% on semaglutide. This is the clearest available evidence, because both groups were studied in the same trial.

Tirzepatide (Mounjaro / Zepbound)

Tirzepatide is a dual GLP-1/GIP agonist. As Mounjaro it is approved for type 2 diabetes; as Zepbound it is approved for chronic weight management. It is a once-weekly subcutaneous injection, started at 2.5 mg and escalated gradually under a provider's direction. Beyond weight loss, trials have shown improvements across cardiometabolic measures such as blood pressure, HbA1c, and lipids.

Semaglutide (Ozempic / Wegovy / Rybelsus)

Semaglutide is a GLP-1 agonist with the longest track record of the two. Ozempic is approved for type 2 diabetes (with a cardiovascular risk-reduction indication in certain patients), Wegovy for chronic weight management, and Rybelsus is an oral tablet for diabetes. The injectables are dosed once weekly and titrated gradually: Wegovy toward 2.4 mg weekly, Ozempic toward up to 2 mg weekly. Semaglutide has extensive cardiovascular outcome data supporting its use.

Are the side effects different?

Both share the incretin-class profile dominated by gastrointestinal effects, mostly during dose escalation. In practice, semaglutide tends toward nausea and constipation, while tirzepatide more commonly causes diarrhea with somewhat less nausea. Both carry class warnings and precautions that are detailed in their FDA labeling and should be reviewed with a provider.

Which should I choose?

That is a decision for you and your healthcare provider, based on your diagnosis (diabetes vs weight management), medical history, insurance coverage, tolerability, and availability. The head-to-head data favor tirzepatide for average weight loss, but semaglutide has the longer track record and an oral option, and individual responses and side effects vary widely. There is no one-size-fits-all answer.

Medical Disclaimer

This page is general educational information, not medical advice. The dosing figures above describe approved labeling and published trials and are not recommendations for any individual. RetaPal is a private tracking and reminder app only. It does not recommend, calculate, or suggest doses. Always follow the dose and schedule given by your own prescriber, and consult your healthcare provider before starting, stopping, or changing any medication.

If your provider has you on a weekly injection, RetaPal can log each dose and count down to your next one, privately, offline, and without ever suggesting a dose.