Mounjaro vs Wegovy

Key differences

People often weigh these two for weight loss, but their US labels give them different jobs. Mounjaro is a diabetes medicine and Wegovy is a weight medicine.¹² They also contain different molecules, made by different companies.¹²

Two different molecules

Mounjaro contains tirzepatide, which activates two hormone receptors, GIP and GLP-1.¹ Wegovy contains semaglutide, which acts on the GLP-1 receptor alone.² Both injections are given once a week, and Wegovy also comes as a once-daily tablet.¹² Half of a tirzepatide dose is cleared in about 5 days; for semaglutide that takes about a week.¹² In both labels, insulin release rises and glucagon falls in a glucose-dependent way, and stomach emptying slows.¹²

Approved for different conditions

Weight loss is not a US indication for Mounjaro.¹ Its label covers blood sugar control in type 2 diabetes, in adults and children 10 and older.¹ Since August 2026 it also covers lowering the risk of heart attack, stroke or cardiovascular death in high-risk adults with type 2 diabetes.¹⁵ Eli Lilly's tirzepatide brand for weight reduction is Zepbound.⁷

Wegovy is the reverse. It is approved for long-term weight reduction in adults, and on the injection in children 12 and older with obesity, but it has no blood sugar indication for type 2 diabetes.² Its other uses are lowering heart event risk in adults with established cardiovascular disease and obesity or overweight, and treating noncirrhotic MASH, a fatty liver disease, with moderate to advanced fibrosis in adults.²

Heart outcome trials

Both labels now include a heart indication, built on trials of different design. Mounjaro's rests on SURPASS-CVOT, which compared it with dulaglutide, a GLP-1 diabetes drug with its own heart indication, in 13,299 adults with type 2 diabetes and established cardiovascular disease.¹ Over a median of 210 weeks, a first major heart event occurred in 12.1% on Mounjaro and 13.0% on dulaglutide.¹ The result showed Mounjaro was not worse; it did not show it was better.¹

Wegovy's rests on SELECT, a placebo-controlled trial of 17,604 adults aged 45 or older with established cardiovascular disease and a BMI of 27 or more, none with diabetes.²⁸ Over a median of 41.8 months, a first major heart event occurred in 6.5% on Wegovy 2.4 mg and 8.0% on placebo.²⁸ One trial used an active drug as the comparison and the other a placebo, and the patients differed, so the two results cannot be ranked against each other.

Weight: label trials and the head-to-head

Each label reports weight, in different patients. In Mounjaro's diabetes trials, adults lost about 5.4 to 11.3 kg over 40 to 52 weeks on 5 to 15 mg.¹ In Wegovy's STEP 1 trial of 1,961 adults without diabetes, average weight fell 14.9% on 2.4 mg and 2.4% on placebo over 68 weeks.²⁹ In a 72-week trial of 1,407 adults with obesity and no diabetes, it fell 18.8% on 7.2 mg, 15.5% on 2.4 mg and 3.9% on placebo.²

The direct comparison was run in obesity, not diabetes. SURMOUNT-5, an open-label trial, randomized 751 adults with obesity but without type 2 diabetes to the highest weekly dose each tolerated of tirzepatide (10 or 15 mg) or semaglutide (1.7 or 2.4 mg) for 72 weeks.⁶ Average weight fell 20.2% with tirzepatide and 13.7% with semaglutide, and waist size shrank 18.4 cm against 13.0 cm.⁶ Stomach and gut problems were the most common side effects in both groups, mostly mild to moderate and mainly during dose escalation.⁶ The semaglutide arm stopped at 2.4 mg, below the 7.2 mg dose the Wegovy label now allows for some adults.⁶²

Doses, devices and daily routine

The dose numbers sit on different scales. Mounjaro climbs from 2.5 mg to as much as 15 mg a week.¹ Wegovy climbs from 0.25 mg to 2.4 mg, with 7.2 mg the adult maximum for weight reduction.² Each label raises the dose in steps to reduce the risk of stomach side effects, and the prescriber sets each step.¹² Since August 2026, the Mounjaro label also allows the 2.5 mg starting dose to be kept as an ongoing dose for blood sugar control.⁵

A missed Mounjaro dose can be taken within 4 days.¹ A missed Wegovy injection is taken only if the next dose is more than 2 days away.²

The devices differ. Mounjaro comes as single-dose pens, single-dose vials, multi-dose vials used with a syringe, and a KwikPen holding 4 weekly doses.¹ Wegovy comes as single-dose pens and syringes, a FlexTouch pen holding four 2.4 mg doses, and once-daily tablets.² Mounjaro has no tablet form.¹ Out of the fridge, a Mounjaro single-dose pen can be kept up to 21 days at up to 86°F; a Wegovy single-dose pen, before its cap comes off, up to 28 days at 46 to 86°F.¹²

The Mounjaro label adds a step for birth control pills: a non-oral or added barrier method for 4 weeks after starting and after each dose increase.¹ The Wegovy label notes more generally that slower stomach emptying can change how other oral medicines are absorbed.²

Side effects

The pattern is shared and the rates differ. In Mounjaro's pooled diabetes trials, nausea affected 12% to 18% on 5 to 15 mg, against 4% on placebo.¹ In Wegovy's adult weight trials at 2.4 mg, nausea affected 44% against 16%, and vomiting 24% against 6%.² These rates come from separate trials in different patients and do not form a head-to-head result.

Both labels carry the boxed warning for thyroid C-cell tumors seen in rodents, and both rule out use with a personal or family history of medullary thyroid carcinoma or with MEN 2.¹² Both list pancreatitis, gallbladder disease and kidney injury from dehydration among their warnings.¹² Both are prescription only in the US.³⁴

Which page to read next

The Mounjaro profile and the Wegovy profile hold each label in full. For results by goal, see Mounjaro and blood sugar, Mounjaro and weight loss and Wegovy and weight loss. Lilly's weight brand has its own page, the Zepbound profile. Nearby pairs are Ozempic vs Wegovy and Mounjaro vs Ozempic, and the GLP-1 comparisons page lists the rest.