Semaglutide vs Tirzepatide: The Real Differences

Key takeaways

• Semaglutide activates one receptor, GLP-1. Tirzepatide is a single peptide that activates two, GIP and GLP-1. That is the whole chemical difference; everything else follows from it or from the labels.
• Head to head, tirzepatide did more: 20.2% versus 13.7% weight loss over 72 weeks in obesity, and larger HbA1c drops (2.01 to 2.30 points versus 1.86) in type 2 diabetes.
• Side effects are the same family. Label rates differ because they come from different trials; in the trials that gave both drugs to the same people, nausea and diarrhea were similar.
• Semaglutide is sold as Ozempic, Wegovy and Rybelsus; tirzepatide as Mounjaro and Zepbound. Semaglutide has more proven outcomes beyond weight and a pill; tirzepatide has a sleep-apnea indication.
• Cash prices in October 2026 overlap: Wegovy $349 a month, Zepbound $299 to $449.

The difference between semaglutide and tirzepatide is one receptor versus two: semaglutide (Ozempic, Wegovy, Rybelsus) activates the GLP-1 receptor, while tirzepatide (Mounjaro, Zepbound) activates both the GIP and GLP-1 receptors. In the trials that compared them directly, tirzepatide produced more weight loss and larger blood-sugar reductions, with similar gastrointestinal side effects. Semaglutide has more outcome data beyond weight, a liver indication and a pill. For the brand-by-brand decision, see our Zepbound vs Wegovy comparison; for the diabetes brands, tirzepatide vs Ozempic.

The differences at a glance

Sources: the five current labels (Wegovy label) (Ozempic label) (Rybelsus and Ozempic tablets label) (Zepbound label) (Mounjaro label), the trials cited below, and our cost guide.

One receptor versus two

GLP-1 and GIP are incretins, gut hormones released after a meal that tell the pancreas to release insulin when glucose is high; GLP-1 also suppresses glucagon, slows the stomach and acts on appetite centers in the brain. Semaglutide is a long-acting copy of GLP-1: its label describes a 94% sequence match to the human hormone, a change at position 8 that blocks the enzyme that normally destroys GLP-1 within minutes, and a fatty acid that binds albumin so one dose lasts about a week (Wegovy label).

Tirzepatide starts from the other hormone. Its label describes a peptide built on the GIP sequence and engineered to activate both receptors, with a 20-carbon fatty acid for a half-life of about five to six days. The label notes that nonclinical studies suggest GIP may add to the control of food intake, and that both receptors sit in appetite-regulating areas of the brain (Zepbound label). Exactly why adding GIP produces more weight loss is still debated; that it does, at the doses tested, is not.

The head-to-head numbers

Obesity: SURMOUNT-5. 751 adults with obesity and no diabetes took the maximum tolerated dose of tirzepatide (10 or 15 mg) or semaglutide (1.7 or 2.4 mg) weekly for 72 weeks. Weight fell 20.2% versus 13.7%, waist circumference 18.4 cm versus 13.0 cm, and more tirzepatide participants reached every threshold from 10% to 25% loss. Gastrointestinal events were the most common in both groups, mostly mild to moderate and during dose escalation (Aronne 2025).

Type 2 diabetes: SURPASS-2. 1,879 adults with type 2 diabetes took tirzepatide 5, 10 or 15 mg or semaglutide 1 mg (an Ozempic dose; Ozempic now goes to 2 mg and Wegovy to 2.4 mg and beyond) for 40 weeks. HbA1c fell 2.01, 2.24 and 2.30 percentage points with tirzepatide versus 1.86 with semaglutide, and tirzepatide produced 1.9, 3.6 and 5.5 kg more weight loss. Nausea affected 17 to 22% versus 18%, diarrhea 13 to 16% versus 12%, and vomiting 6 to 10% versus 8%; serious adverse events were reported by 5 to 7% versus 3% (Frías 2021). Both trials were open-label and funded by Lilly.

What neither trial tested: tirzepatide against semaglutide 7.2 mg, or long-term outcomes such as heart attacks. On outcomes, semaglutide is ahead on evidence. In SELECT, 17,604 adults with heart disease and overweight or obesity, without diabetes, had cardiovascular death, heart attack or stroke in 6.5% on semaglutide 2.4 mg versus 8.0% on placebo (Lincoff 2023), and Ozempic carries cardiovascular and kidney indications in type 2 diabetes (Ozempic label). Tirzepatide's cardiovascular trial compared it with another GLP-1 drug, dulaglutide, in type 2 diabetes and showed it was non-inferior; that result added a cardiovascular indication to Mounjaro's label in August 2026 (Mounjaro label).

Side effects: what actually differs

On the weight-loss labels, nausea was reported by 44% on semaglutide 2.4 mg (16% on placebo) and by 25 to 29% on tirzepatide 5 to 15 mg (8% on placebo); vomiting by 24% versus 8 to 13% (Wegovy label) (Zepbound label). Those are separate trial programs with different populations and methods, and the labels warn against comparing them. Where the two drugs met in the same trial, the gap closed: nausea was similar in SURPASS-2, and in SURMOUNT-5 it affected 44% of both groups, as our Zepbound vs Wegovy comparison shows from the trial's posted results.

The differences that do hold up:

• Injection-site reactions are more common with tirzepatide: 6 to 8% versus 2% on placebo in the Zepbound trials.
• Oral contraceptives. Tirzepatide reduces their absorption; the label advises a non-oral or added barrier method for four weeks after starting and after each dose increase.
• Pregnancy planning. Because semaglutide lingers for five to seven weeks, the Wegovy label says to stop at least two months before a planned pregnancy.
• High-dose semaglutide. At 7.2 mg, abnormal skin sensations (dysesthesia) were reported by 22%, against 6% on 2.4 mg.

Everything else is shared, from the boxed warning on thyroid C-cell tumors in rodents to pancreatitis, gallbladder disease and aspiration under anesthesia. Our GLP-1 side effects guide has the full label table.

Dosing schedules

Both drugs are weekly injections titrated every four weeks to limit nausea. These are the label schedules, not recommendations; your prescription overrides them.

The oral semaglutide label warns that Rybelsus and Ozempic tablets are not interchangeable milligram for milligram (Rybelsus and Ozempic tablets label). Neither drug has a conversion chart to the other. Full charts: semaglutide dosage chart and tirzepatide dosage chart. If a compounded vial is involved, the milligram dose has to be converted to syringe units with the peptide calculator.

Which brand is which

Same molecule, different label means different insurance rules. A diabetes brand prescribed only for weight is off-label, and coverage for the diabetes brands is generally tied to a diabetes diagnosis; tirzepatide vs Ozempic covers that case.

Price differences

Paying cash in October 2026, Zepbound costs $299 at 2.5 mg, $399 at 5 mg and $449 at 7.5 to 15 mg through Lilly's self-pay program, against $349 for Wegovy through Novo Nordisk's pharmacy, so Zepbound is cheaper at the starting doses and Wegovy at maintenance. Mounjaro is not in Lilly's program and lists at about $1,112; Ozempic is $350 on TrumpRx (cost guide). Compounded versions cost less but are legal only for a documented individual need since the shortages ended; see compounded semaglutide vs tirzepatide and the tirzepatide cost guide.

Bottom line

Tirzepatide hits two receptors and produces more weight loss and glucose lowering than semaglutide in direct comparisons, with similar stomach side effects. Semaglutide hits one, has the longer record of hard outcomes, a liver indication and pills. The brand name tells you the label, not the molecule: Ozempic and Wegovy are semaglutide, Mounjaro and Zepbound are tirzepatide.

Frequently asked questions

+−What is the difference between semaglutide and tirzepatide?

Semaglutide (Ozempic, Wegovy, Rybelsus) activates one hormone receptor, GLP-1. Tirzepatide (Mounjaro, Zepbound) is a single peptide that activates two, GIP and GLP-1. In head-to-head trials tirzepatide produced more weight loss (20.2% versus 13.7% over 72 weeks in obesity) and larger blood-sugar reductions in type 2 diabetes. Semaglutide has more proven outcomes beyond weight, including fewer heart attacks and strokes in people with heart disease and obesity, and it comes as a pill.

+−Is tirzepatide stronger than semaglutide?

For weight loss and glucose lowering, yes at the doses tested. In SURMOUNT-5, adults with obesity lost 20.2% on tirzepatide 10 or 15 mg versus 13.7% on semaglutide 1.7 or 2.4 mg. In SURPASS-2, people with type 2 diabetes lowered HbA1c by 2.01 to 2.30 points on tirzepatide 5 to 15 mg versus 1.86 on semaglutide 1 mg, and lost 1.9 to 5.5 kg more. 'Stronger' does not mean better for everyone; semaglutide has the obesity cardiovascular-outcome data.

+−Is Mounjaro the same as Zepbound?

Same molecule, different label. Both are tirzepatide from Eli Lilly at the same doses. Mounjaro is approved for type 2 diabetes (and, since August 2026, to reduce cardiovascular events in people with diabetes at high risk); Zepbound for weight management and obstructive sleep apnea. The same applies to Ozempic and Wegovy, which are both semaglutide. The label matters for insurance and price: Zepbound is in Lilly's self-pay program, Mounjaro is not.

+−What category of drug is semaglutide?

Semaglutide is a GLP-1 receptor agonist: a modified version of the human gut hormone GLP-1, 94% identical in sequence, with a fatty-acid chain that makes it last about a week. Tirzepatide is classed separately as a dual GIP and GLP-1 receptor agonist. Both are peptides, which is why the injectable forms are weekly shots and the semaglutide pill needs an absorption enhancer.

+−What is the chemical structure of tirzepatide?

According to its label, tirzepatide is a peptide built on the GIP sequence, with aminoisobutyric acid at positions 2 and 13, a C-terminal amide, and a lysine at position 20 attached through a linker to a 20-carbon fatty diacid that binds albumin and stretches the half-life to about five to six days. Its molecular weight is 4,813.53 daltons, against 4,113.58 for semaglutide.

+−Does tirzepatide or semaglutide cause more hair loss?

The rates are close. On the labels, hair loss affected 4 to 5% on tirzepatide versus 1% on placebo and 3% on semaglutide 2.4 mg versus 1%. In SURMOUNT-5, which gave both drugs to the same population, it was reported by 8% on tirzepatide and 6% on semaglutide. Both labels tie it to rapid weight loss, and it affected women far more than men.

+−Can you take semaglutide and tirzepatide together?

No. Both labels say they should not be combined with any other GLP-1 receptor agonist, and tirzepatide already includes GLP-1 activity. Switching from one to the other is a replacement, not an addition, and neither label contains a dose-conversion chart.

Sources

1. StudyAronne LJ et al. Tirzepatide as compared with semaglutide for the treatment of obesity (SURMOUNT-5). N Engl J Med 2025;393:26-36. (2025)
2. StudyFrías JP et al. Tirzepatide versus semaglutide once weekly in patients with type 2 diabetes (SURPASS-2). N Engl J Med 2021;385:503-15. (2021)
3. StudyLincoff AM et al. Semaglutide and cardiovascular outcomes in obesity without diabetes (SELECT). N Engl J Med 2023;389:2221-32. (2023)
4. LabelNovo Nordisk. Wegovy (semaglutide) injection and tablets: prescribing information, revised June 2026 (DailyMed setid ee06186f-2aa3-4990-a760-757579d8f77b). (2026)
5. LabelEli Lilly. Zepbound (tirzepatide) injection: prescribing information, revised August 2026 (DailyMed setid 487cd7e7-434c-4925-99fa-aa80b1cc776b). (2026)
6. LabelNovo Nordisk. Ozempic (semaglutide) injection: prescribing information, revised June 2026 (DailyMed setid adec4fd2-6858-4c99-91d4-531f5f2a2d79). (2026)
7. LabelEli Lilly. Mounjaro (tirzepatide) injection: prescribing information, revised August 2026 (DailyMed setid d2d7da5d-ad07-4228-955f-cf7e355c8cc0). (2026)
8. LabelNovo Nordisk. Rybelsus and Ozempic (semaglutide) tablets: prescribing information, revised January 2026 (DailyMed setid 27f15fac-7d98-4114-a2ec-92494a91da98). (2026)