Tirzepatide vs Semaglutide for Weight Loss: A Clinical Comparison

When people compare tirzepatide vs semaglutide for weight loss, the short answer from the only direct head-to-head obesity trial is that tirzepatide produced greater average weight loss than semaglutide — about -20.2% versus -13.7% of body weight over 72 weeks. Both are FDA-approved injectable prescription medicines that differ in how they work: tirzepatide activates two gut-hormone receptors (GIP and GLP-1), while semaglutide activates one (GLP-1). The rest comes down to dosing, tolerability, indications, and what a licensed provider thinks fits your health profile. This is educational information, not medical advice.

What is the difference between tirzepatide and semaglutide?

The two drugs share a family resemblance but are not the same molecule. According to the SURMOUNT-5 publication (NEJM, 2025) and the FDA labels, tirzepatide is a dual agonist that binds and activates both the GIP (glucose-dependent insulinotropic polypeptide) receptor and the GLP-1 (glucagon-like peptide-1) receptor. Semaglutide is a GLP-1 receptor agonist only. That single-versus-dual mechanism is the core pharmacological distinction between them.

Brand names matter here, and the pairings are exact. Zepbound and Mounjaro are both tirzepatide from Eli Lilly: Zepbound was FDA-approved for chronic weight management on November 8, 2023, and Mounjaro is approved for type 2 diabetes. Wegovy and Ozempic are both semaglutide from Novo Nordisk: Wegovy was FDA-approved for weight management on June 4, 2021, and Ozempic is approved for type 2 diabetes. In December 2024, Zepbound also became the first prescription medicine FDA-approved for moderate-to-severe obstructive sleep apnea in adults with obesity. If you are weighing peptide-based options more broadly, our overview of peptides for weight loss adds context.

Which works better for weight loss, tirzepatide or semaglutide?

The most reliable comparison comes from SURMOUNT-5, a phase 3b, open-label, 72-week head-to-head trial in 751 adults with obesity but without type 2 diabetes, using the maximum tolerated dose of each drug. At week 72, tirzepatide produced a mean body-weight change of -20.2% compared with -13.7% for semaglutide (p<0.001). In absolute terms, that was roughly 22.8 kg versus 15.0 kg of mean weight loss, with waist-circumference reductions of -18.4 cm versus -13.0 cm. These are averages across a specific trial population over a defined period — they are not a promise of any individual outcome, and individual results vary.

Responder data reported in trade coverage of SURMOUNT-5 followed the same direction: as reported by TCTMD, more participants on tirzepatide reached at least 10% loss (over 80% vs 60.5% for semaglutide) and at least 20% loss (about 50% vs 27.3%). Some of those figures are approximate secondary reporting; the NEJM primary numbers (-20.2% vs -13.7%) are the headline result to rely on.

It is worth being clear about what each placebo-controlled trial showed on its own, since these are not direct comparisons. In SURMOUNT-1 (tirzepatide monotherapy, 2,539 adults with obesity/overweight without diabetes, 72 weeks), mean weight loss was 16.0% at 5 mg, 21.4% at 10 mg, and 22.5% at 15 mg, versus 2.4% for placebo. In STEP-1 (semaglutide 2.4 mg, 1,961 adults with obesity/overweight without diabetes, 68 weeks), mean weight loss was 14.9% versus 2.4% for placebo, and 86.4% of participants lost at least 5% of body weight. Because these used different populations, designs, and comparators, the STEP-1 and SURMOUNT-1 numbers should not be read side by side as a head-to-head.

How do tirzepatide and semaglutide compare in diabetes trials?

Outside obesity, the head-to-head SURPASS-2 trial (1,879 adults with type 2 diabetes on metformin, 40 weeks) found tirzepatide (5/10/15 mg) achieved superior A1c and body-weight reductions versus semaglutide 1 mg. Weight loss was -7.6 kg, -9.3 kg, and -11.2 kg for tirzepatide versus -5.7 kg for semaglutide (treatment-regimen estimand). Important caveat: these are diabetes figures at lower doses (semaglutide 1 mg, not the 2.4 mg used for weight management), so they are not interchangeable with the obesity outcomes above.

What are the side effects of tirzepatide and semaglutide?

For both drugs, the most common adverse events are gastrointestinal — nausea, diarrhea, vomiting, and constipation — and they are generally mild-to-moderate and concentrated during dose escalation. In SURMOUNT-5, GI events were the most frequent in both groups; discontinuation due to GI events was 2.7% with tirzepatide versus 5.6% with semaglutide, with overall adverse-event discontinuation of 6.1% versus 8.0%.

The table below shows label adverse-reaction rates. These come from separate clinical-trial programs, so they are label data — not a direct head-to-head measure of tolerability.

Adverse reaction	Zepbound (tirzepatide), 5/10/15 mg	Wegovy (semaglutide)
Nausea	25% / 29% / 28%	44%
Diarrhea	19% / 21% / 23%	30%
Vomiting	8% / 11% / 13%	24%
Constipation	up to ~17%	24%
Abdominal pain	—	20%

Sources: Zepbound FDA label (pooled obesity trial data) and the Wegovy DailyMed label (pooled trial data). Both drugs also carry a boxed warning for the risk of thyroid C-cell tumors, based on rodent studies — human relevance has not been determined — and both are contraindicated in people with a personal or family history of medullary thyroid carcinoma (MTC) or Multiple Endocrine Neoplasia syndrome type 2 (MEN 2). Labeling also flags risks such as pancreatitis and gallbladder disease, which is one reason these medicines require provider supervision.

How are tirzepatide and semaglutide dosed?

Both are once-weekly subcutaneous injections that start low and titrate up. Per the Zepbound prescribing information, tirzepatide starts at 2.5 mg once weekly for 4 weeks, then increases by 2.5 mg every 4 weeks as tolerated, with maintenance doses of 5, 10, or 15 mg and six strengths available (2.5/5/7.5/10/12.5/15 mg). Per the Wegovy label, semaglutide follows a 16-week escalation — 0.25 mg (weeks 1–4), 0.5 mg (5–8), 1 mg (9–12), 1.7 mg (13–16) — then a maintenance dose of 1.7 or 2.4 mg once weekly. For a closer look at titration, see our tirzepatide dosage chart.

	Tirzepatide (Zepbound)	Semaglutide (Wegovy)
Mechanism	Dual GIP + GLP-1 agonist	GLP-1 agonist
Manufacturer	Eli Lilly	Novo Nordisk
Obesity approval	Nov 8, 2023	Jun 4, 2021
Head-to-head result (SURMOUNT-5)	-20.2% at 72 wks	-13.7% at 72 wks
Dosing	Weekly; 5/10/15 mg maintenance	Weekly; 1.7 or 2.4 mg maintenance

Are compounded versions of these drugs available?

Be cautious here. Compounded semaglutide and tirzepatide are not FDA-approved; the FDA has not evaluated them for safety, quality, or efficacy, and they are not equivalent to the FDA-approved branded products. They are prescription only. The earlier national shortages have been resolved: the FDA removed tirzepatide from the shortage list in October 2024 (resolution finalized December 19, 2024) and declared the semaglutide shortage resolved on February 21, 2025, with all compounding enforcement-discretion grace periods ending by May 2025. Separately, on April 30, 2026, the FDA proposed to exclude semaglutide, tirzepatide, and liraglutide from the 503B bulks list. The practical upshot for 2026 is that mass compounding of these drugs is no longer routinely permitted, so do not assume compounded GLP-1s are freely available.

How do I decide which is right for me?

That is a conversation for a licensed provider, not a self-diagnosis. The choice depends on your medical history, contraindications, other medications, insurance and access, side-effect tolerance, and goals — all of which are weighed alongside lifestyle changes, since both drugs are studied and labeled for use with a reduced-calorie diet and increased physical activity. If you are exploring whether a GLP-1 or dual agonist fits into a broader plan, our guide on how it works walks through the evaluation process, and you can review pricing before you start.

Frequently asked questions

Is tirzepatide stronger than semaglutide for weight loss?

In the SURMOUNT-5 head-to-head trial, tirzepatide produced a greater average weight reduction than semaglutide (-20.2% vs -13.7% over 72 weeks at maximum tolerated doses). These are trial averages in adults with obesity without diabetes, and individual results vary.

Are Zepbound, Mounjaro, Wegovy, and Ozempic the same drug?

No. Zepbound and Mounjaro are both tirzepatide (Eli Lilly) — Zepbound for obesity/OSA, Mounjaro for type 2 diabetes. Wegovy and Ozempic are both semaglutide (Novo Nordisk) — Wegovy for weight management, Ozempic for type 2 diabetes.

Which has fewer side effects?

Both most commonly cause gastrointestinal effects that cluster during dose escalation. In SURMOUNT-5, discontinuation due to GI events was lower with tirzepatide (2.7%) than semaglutide (5.6%). Label nausea rates come from separate trials and are not a direct head-to-head, so discuss tolerability with your provider.

Do these drugs cause thyroid cancer?

Both carry a boxed warning for thyroid C-cell tumors based on rodent studies; human relevance has not been determined. They are contraindicated in people with a personal or family history of medullary thyroid carcinoma or MEN 2. Talk to a provider about your history.

Can I still get compounded semaglutide or tirzepatide?

Compounded versions are not FDA-approved and have not been evaluated by the FDA for safety, quality, or efficacy. With the shortages resolved (tirzepatide in late 2024, semaglutide on February 21, 2025), routine mass compounding is no longer permitted, so do not assume they are freely available.

How long does it take to see results?

Both drugs are titrated over weeks, and the pivotal trials measured outcomes at 68–72 weeks. There is no guaranteed timeline or amount of weight loss; results are framed as averages in trial populations, and individual results vary.