Semaglutide vs Tirzepatide: Which Works Better for Weight Loss?

Semaglutide and tirzepatide are different molecules: tirzepatide is a dual GIP receptor and GLP-1 receptor agonist, while semaglutide acts on the GLP-1 receptor only.

Each has a weight-management brand and a diabetes brand, and the labels split them by use: semaglutide is Wegovy for weight management and Ozempic for type 2 diabetes (Novo Nordisk also sells oral semaglutide for type 2 diabetes as Ozempic tablets and Rybelsus); tirzepatide is Zepbound for weight management and moderate-to-severe obstructive sleep apnea, and Mounjaro for type 2 diabetes.

Wegovy (Novo Nordisk) is approved, with diet and activity, for chronic weight management in adults with obesity, adults with overweight plus a weight-related condition, and patients 12 and older with obesity; its label also covers cardiovascular risk reduction in adults with established cardiovascular disease and obesity or overweight and, under accelerated approval, MASH with F2–F3 fibrosis.

It comes as a once-weekly injection, and a once-daily tablet is now also approved for adults.

Zepbound (Eli Lilly) is a once-weekly injection approved for chronic weight management in adults with obesity or overweight plus a weight-related condition, and for moderate-to-severe obstructive sleep apnea in adults with obesity.

It is not approved for adolescents.

Using Ozempic or Mounjaro for weight loss without type 2 diabetes is off-label: that use is not on any current US label for either product.

A third option was first approved in the US in 2026: Foundayo (orforglipron), a once-daily oral GLP-1 drug that is neither semaglutide nor tirzepatide.

The direct comparison is SURMOUNT-5, published in the New England Journal of Medicine in 2025: 751 adults with obesity and no type 2 diabetes took tirzepatide (10 or 15 mg weekly) or semaglutide (1.7 or 2.4 mg weekly) for 72 weeks.

Mean weight loss at week 72 was 20.2% with tirzepatide and 13.7% with semaglutide; mean waist reduction was 18.4 cm versus 13.0 cm.

On that average, tirzepatide produced the larger weight loss.

Three limits matter: the trial was open-label, so participants knew which drug they got; it was funded by Eli Lilly, tirzepatide's maker; and the semaglutide arm was capped at 2.4 mg, the label's usual maintenance dose — the 7.2 mg Wegovy HD dose added in 2026 was not studied.

We could not confirm a published head-to-head trial that includes the Wegovy tablet, the 7.2 mg dose, or people with type 2 diabetes.

The figures are trial means, not a prediction for any one person.

In the head-to-head trial, the most common side effects in both groups were gastrointestinal, mostly mild to moderate and mainly during dose escalation.

Each label's own trial rates cannot be ranked against the other's: the trials had different populations and designs.

In Zepbound's weight trials, nausea was reported by 25% on 5 mg, 29% on 10 mg and 28% on 15 mg, versus 8% on placebo; its label lists nausea, diarrhea, vomiting, constipation and abdominal pain among reactions reported by at least 5% of patients.

On Wegovy's side, in its adult weight trials of the injection, nausea was reported by 44% of patients on the 2.4 mg dose versus 16% on placebo, and 73% reported gastrointestinal side effects overall versus 47% on placebo.

Side effects lead some patients to stop: 6.8% of Wegovy 2.4 mg patients stopped permanently because of adverse reactions versus 3.2% on placebo, most often nausea, vomiting or diarrhea.

The warning lists reach beyond the gut: Zepbound's includes severe gastrointestinal reactions (not recommended in severe gastroparesis), acute kidney injury from dehydration, gallbladder disease, acute pancreatitis, serious allergic reactions, and low blood sugar with insulin or sulfonylureas.

Wegovy's label reports gallstones in 1.6% of injection patients versus 0.7% on placebo and confirmed acute pancreatitis in 4 treated patients (0.2 cases per 100 patient-years) versus 1 on placebo, and warns of acute kidney injury, severe gastrointestinal reactions, hypersensitivity, diabetic retinopathy complications, heart-rate increase and aspiration under anesthesia.

Each drug's full warning list is on its own guide — the semaglutide guide for Wegovy, the tirzepatide guide for Zepbound.

Both drugs are priced per month of supply; the figures below are each maker's published self-pay prices, read October 16, 2026.

The lists are built differently: Novo Nordisk charges one price across Wegovy injection doses (0.25–2.4 mg), while Eli Lilly's Zepbound price rises with dose, $299 at 2.5 mg to $699 at 10–15 mg — so the label's usual maintenance doses work out to $349 a month for Wegovy injection and $399–$699 for Zepbound (maintenance doses 5, 10 or 15 mg).

A clinic's program fee is separate, and we could not confirm a national program figure — ask what each fee includes: which product, at which dose, which visits or labs.

Some programs advertise lower prices by dispensing compounded copies instead of the brands.

Compounded drugs are not FDA-approved and are not reviewed for safety, effectiveness or quality before marketing, and FDA says they should be used only when a patient's needs cannot be met by an FDA-approved drug.

FDA lists claiming a compounded drug is "the same as" an FDA-approved drug among its red flags — our compounded GLP-1s guide covers that market.

IRS Publication 502 counts weight-loss expenses as medical expenses when a program treats a specific physician-diagnosed disease such as obesity, hypertension or heart disease; whether a program fee qualifies depends on your situation.

That decision belongs to you and a licensed prescriber who has evaluated your health history.

The labels cover different populations: Wegovy's weight indication includes patients 12 and older with obesity, while Zepbound is approved for adults only.

Zepbound's label adds an approval Wegovy's does not name — moderate-to-severe obstructive sleep apnea in adults with obesity — while Wegovy's adds cardiovascular risk reduction and accelerated approval for MASH with F2–F3 fibrosis.

The forms differ too: Wegovy comes as a weekly injection or a once-daily tablet for adults; Zepbound is a once-weekly injection.

If a program offers "Ozempic" or "Mounjaro" for weight loss, note those brands' labels are for type 2 diabetes, so using them for weight without diabetes is off-label.

Both drugs sit inside the broader field of medical weight loss, where a licensed prescriber manages the prescription alongside diet and activity changes, and FDA advises filling any prescription at a state-licensed pharmacy.

The labels do not describe how to switch: neither gives a protocol, and both advise against combining Wegovy or Zepbound with any other GLP-1 receptor agonist or another product containing the same drug.

No FDA label provides a semaglutide-to-tirzepatide dose conversion, and the Ozempic label even states that two semaglutide tablet products (Rybelsus and Ozempic tablets) are not substitutable on a milligram-to-milligram basis.

What each label gives is its own schedule: Wegovy injection starts at 0.25 mg weekly, titrated every 4 weeks, with 2.4 mg the usual maintenance dose and 7.2 mg the maximum after at least 4 weeks of tolerating 2.4 mg when more weight reduction is needed.

Zepbound starts at 2.5 mg weekly for 4 weeks — a starter dose only — then rises in 2.5 mg steps at least 4 weeks apart, with maintenance doses of 5, 10 or 15 mg.

No label translates one schedule into the other, so how a switch is sequenced is a decision for the prescribing clinician who knows your history.

Both drugs are prescription-only: FDA advises a prescription from a licensed prescriber, filled at a state-licensed pharmacy, and flags sellers that do not require a screening and prescription.

As of FDA's April 1, 2026 update, neither tirzepatide nor semaglutide is on the agency's drug shortage list or the 503B bulks list.

The first question for any clinic is which product it dispenses — the brand-name drug or a compounded copy.

FDA's red-flag list for GLP-1 sellers includes deep discounts that seem too good to be true, no screening and prescription by a licensed doctor, no doctor available for questions, label spelling errors or wrong pharmacy addresses, and a pharmacy name you suspect is fraudulent.

FDA has also warned about counterfeit Ozempic in the US supply chain and about fraudulent compounded semaglutide and tirzepatide whose labels name pharmacies that do not exist or did not make the product.

We found no data on which med spas offer which drug, so ask each clinic what it dispenses, who prescribes and what the fee covers — our guide to choosing a med spa covers the credentials and questions in depth.