Ozempic vs Mounjaro (and Zepbound): Real Differences From the Trials and Labels

Ozempic and Mounjaro are different molecules with different approved uses. Ozempic is semaglutide, which switches on the receptor for a gut hormone called GLP-1^[1]. Mounjaro is tirzepatide, which switches on two receptors, GIP and GLP-1^[4]. In the US, both are approved only for type 2 diabetes^[1,4]. For weight management, the fair comparison is Wegovy (semaglutide) vs. Zepbound (tirzepatide): the same two molecules, under different brand names and labels^[2,5].

The only published head-to-head trial in obesity is SURMOUNT-5: in 751 adults without diabetes, weight fell 20.2% on tirzepatide and 13.7% on semaglutide over 72 weeks^[15]. In type 2 diabetes, SURPASS-2 compared tirzepatide with Ozempic 1 mg for 40 weeks^[17]. Eli Lilly, which makes Mounjaro and Zepbound, funded both, and both were open-label: participants knew which drug they were getting^[15,17]. Which one fits a given person is for their prescriber to decide.

Label facts have a dotted underline and the date I checked them. Weight-loss results are covered in a separate guide, and how these drugs work in what GLP-1 medications are.

Ozempic vs. Mounjaro at a glance

Sources: US labels for Ozempic^[1] and Mounjaro^[4], sections 1, 2 and 12.1.

What each one is

Semaglutide. The US Ozempic label describes it as a GLP-1 analog with 94% sequence homology to human GLP-1^[1]: a tweaked, longer-lasting version of the hormone. Novo Nordisk sells it as Ozempic (weekly injection, type 2 diabetes), Wegovy (weight management; weekly injection or daily tablet) and Rybelsus and Ozempic tablets (daily pills, type 2 diabetes)^[1,2,3].

Tirzepatide. Its US label calls it a GIP receptor and GLP-1 receptor agonist^[4]. GIP (glucose-dependent insulinotropic polypeptide) is another gut hormone that boosts insulin after meals^[43]. Eli Lilly sells it as Mounjaro (type 2 diabetes) and Zepbound (weight management and sleep apnea)^[4,5]. In the EU and Mexico, Mounjaro carries both uses^[8,12,44].

Each active ingredient has its own guide: semaglutide and tirzepatide. If you’re weighing the two weight-management shots, see Zepbound vs. Wegovy.

What each one is approved for in the US, EU and Mexico

Sources: section 1 of the US labels for Ozempic^[1], Rybelsus^[3], Wegovy^[2], Mounjaro^[4] and Zepbound^[5]; section 4.1 of the EU labels for Ozempic^[6], Wegovy^[7] and Mounjaro^[8]; for Mexico, COFEPRIS (2024^[9] and 2023^[10]), Lilly Mexico^[13], the Diario Oficial (July 3, 2026)^[12] and, for the brand name, the 2024 COFEPRIS list of drug registrations^[44], all in Spanish.

The US indications that go beyond blood sugar and weight rest on clinical-outcome trials, which I summarize separately: SUSTAIN-6 and FLOW for Ozempic, SELECT and ESSENCE for Wegovy, SURPASS-CVOT for Mounjaro and SURMOUNT-OSA for Zepbound^{[33,34,35,36,41,42]}. Both molecules have also been tested in people with obesity and heart failure with preserved ejection fraction: semaglutide in STEP-HFpEF and tirzepatide in SUMMIT^[37,38].

What the head-to-head trials show

SURMOUNT-5: Zepbound’s drug vs. Wegovy’s drug in obesity

SURMOUNT-5 enrolled 751 adults with obesity, or overweight plus at least one weight-related condition, and no diabetes^[15]. According to the EU Mounjaro label, they had a mean age of 44.7 years and a mean BMI of 39.4, and 64.7% were women^[8]. Per the trial registry, about one in four (196 of 750) was Hispanic or Latino, at sites in the US and Puerto Rico^[16]. For 72 weeks, each group got its maximum tolerated weekly dose: tirzepatide 15 or 10 mg, or semaglutide 2.4 or 1.7 mg (the Wegovy doses)^[15].

Sources: the trial paper^[15] and, for the waist difference, the registry^[16]. The 95% CI (confidence interval) is the range where the true effect probably lies.

Using a different analysis, the EU Mounjaro label reports −21.6% on tirzepatide and −15.4% on semaglutide (difference −6.2 points; 95% CI −7.8 to −4.6)^[8]. More people on tirzepatide also reached losses of at least 10%, 15%, 20% and 25%^[15]. The US Zepbound label doesn’t include SURMOUNT-5^[5].

Limits: knowing the assigned drug may have shaped adherence and reported side effects; several authors work for Eli Lilly; it excluded diabetes, didn’t test semaglutide 7.2 mg and didn’t measure heart attacks or strokes^[15].

SURPASS-2: Mounjaro vs. Ozempic in type 2 diabetes

SURPASS-2 enrolled 1,879 adults with type 2 diabetes on metformin, with an average HbA1c of 8.28% (HbA1c reflects average blood sugar over the past few months), an average age of 56.6 and an average weight of 93.7 kg (about 207 lb)^[17]. The US Mounjaro label notes that 70% identified as Hispanic or Latino^[4], and its registry^[18] lists eight sites in Mexico. It lasted 40 weeks.

Sources: the trial paper^[17] and Table 5 of the US Mounjaro label, which rounds the HbA1c differences to −0.2, −0.4 and −0.5 points^[4].

The main limitation: the US Ozempic label allows up to 2 mg once weekly^[1], and that dose was never tested against tirzepatide^[17].

Placebo-controlled trials can’t be compared with each other

Each drug’s placebo-controlled trials give numbers that are not comparable across drugs: populations, lengths and methods differ. Without diabetes, semaglutide 2.4 mg lowered weight by 14.9% vs. 2.4% on placebo over 68 weeks (STEP 1; trial summary)^[19], and tirzepatide by 15.0% to 20.9% by dose vs. 3.1% over 72 weeks (SURMOUNT-1; trial summary)^[21]. With type 2 diabetes, losses were smaller: 9.6% vs. 3.4% in STEP 2 (68 weeks; trial summary)^[20] and up to 14.7% vs. 3.2% in SURMOUNT-2 (72 weeks; trial summary)^[22]. Design matters too: in STEP 3, which added intensive behavioral therapy, the placebo group lost 5.7% over 68 weeks^[39], and SURMOUNT-3 only randomized people who had already lost at least 5% with 12 weeks of intensive lifestyle intervention^[40]. More in how much weight people lose.

And semaglutide 7.2 mg

The US Wegovy label now allows up to 7.2 mg once weekly in adults who tolerate 2.4 mg for at least 4 weeks and for whom additional weight reduction is clinically indicated^[2]. In STEP UP (1,407 adults with obesity, no diabetes; trial summary), the label reports weight changes of −18.8% on 7.2 mg, −15.5% on 2.4 mg and −3.9% on placebo at 72 weeks^[2,23]. No published trial has compared this dose with tirzepatide.

Side effects: what can be compared

Comparing side effects fairly takes the same trial:

Sources: SURMOUNT-5 registry^[16], people who got at least one dose, 72 weeks (per-symptom rates count non-serious events); SURPASS-2 abstract^[17], 40 weeks.

Within each trial, nausea and diarrhea were similar. SURMOUNT-5 had less vomiting on tirzepatide, with no published statistical test^[16], and open-label designs affect what gets reported. Don’t compare the two trials with each other. Both papers say most digestive side effects were mild or moderate^[15,17]. These data don’t show that either drug is better tolerated.

What the US labels report

Each US label has its own table from its own placebo-controlled trials, and each warns that rates from one drug’s trials can’t be directly compared with another drug’s^[1,2,4,5]. Read it as context by population, not as a ranking:

Sources: section 6.1 of the US labels. Ozempic^[1], Table 1: two trials, about 33 weeks of exposure on average. Mounjaro^[4], Table 1: SURPASS-1 and SURPASS-5, about 37 weeks. Wegovy^[2], Table 3: three trials of up to 68 weeks. Zepbound^[5], Table 1: SURMOUNT-1 and SURMOUNT-2, up to 72 weeks.

For both molecules, digestive side effects were more common in the weight-management trials. The EU labels use frequency categories instead of percentages. There, nausea and diarrhea are “very common” (more than 1 in 10 people) for Ozempic, Wegovy and Mounjaro. Vomiting, abdominal pain and constipation are “common” (1 in 100 to 1 in 10) for Ozempic and in Mounjaro’s adult diabetes trials, and “very common” for Wegovy and in Mounjaro’s weight-management trials and its SURPASS-CVOT diabetes trial. Acute pancreatitis is “uncommon” (1 in 1,000 to 1 in 100) for all three^[6,7,8].

The warnings overlap. All four US labels carry a boxed warning: thyroid C-cell tumors in rodents, of unknown relevance to humans, and a contraindication in people with a personal or family history of medullary thyroid carcinoma or with MEN 2^[1,2,4,5]. All four also warn about acute pancreatitis, gallbladder disease, kidney injury from dehydration, severe digestive reactions, diabetic retinopathy complications in people with type 2 diabetes, and aspiration during anesthesia or deep sedation^[1,2,4,5]. One practical difference: the Mounjaro and Zepbound labels say tirzepatide may make birth-control pills less effective, and advise switching to a non-oral method, or adding a barrier method, for 4 weeks after starting and for 4 weeks after each dose increase^[4,5]. The semaglutide labels don’t include that advice^[1,2].

If a side effect worries you, bring it up with your doctor. I have guides on what to eat with nausea and on constipation.

Dose steps and how they’re taken

All four are weekly injections under the skin that, per their US labels, can be given at any time of day, with or without meals^[1,2,4,5]. Each label steps the dose up gradually, to reduce digestive side effects:

Source: section 2 of the US labels for Ozempic^[1], Mounjaro^[4], Wegovy^[2] and Zepbound^[5].

Milligrams don’t translate between the two molecules, and no label gives a conversion. Your prescriber decides the dose, the pace of increases and any change to the schedule.

Availability and cost in the US, Spain and Mexico

United States. All four need a prescription. The manufacturers’ US list prices, and what they come to per dose and per month, are in the monthly cost calculator and in Ozempic vs. Wegovy and Mounjaro vs. Zepbound, but what you pay depends on your insurance plan, which may cover a drug for one use and not another. Your plan’s formulary shows what applies to you. Compounded versions aren’t the same: the FDA says compounded drugs aren’t FDA-approved or reviewed for safety, effectiveness or quality^[14].

Spain. Ozempic costs €117.89 per 4-dose pen at the 0.25, 0.5 or 1 mg strengths, per the Nomenclátor (September 2026)^[26]. The public health system reimburses it, with prior authorization, only for adults with type 2 diabetes and a BMI of 30 or more^[27]. Mounjaro isn’t reimbursed^[28] for any use; the consumer group OCU put it at €207.91 to €446.07 per pen, by dose^[29]. Details in the price pages for Ozempic, Mounjaro and Wegovy (in Spanish), and the cost per dose and per month is in the monthly cost calculator.

Mexico. Both need a prescription, as COFEPRIS reminds for Ozempic^[10] and tirzepatide^[11]. There are no official prices: pharmacy prices reported by POSTA ranged from 3,096 to 3,205.50 pesos for an Ozempic 0.25/0.5 mg pen^[30] and from 4,400 to 9,700 pesos for a Mounjaro pen, by dose^[31]. The IMSS list (July 2026) includes neither injectable^[32]. More in the Mexico price pages for Ozempic and Mounjaro (in Spanish); the monthly cost calculator covers Mexico too.

Which is better? Why that’s the wrong question

“Better” has no general answer. Tirzepatide lowered average weight more in SURMOUNT-5^[15], but weight is only one factor:

• The approved use. In the US, EU and Mexico, Ozempic isn’t approved for weight management^[1,6,9].
• Other conditions. In the US, the labels differ beyond blood sugar and weight: kidney disease (Ozempic), MASH (Wegovy), sleep apnea (Zepbound)^[1,2,5]. See the table above.
• Medical history. The labels flag, for example, past pancreatitis or diabetic retinopathy; the tirzepatide labels add the birth-control point^[1,2,4,5].

And an average doesn’t predict what will happen to one person. Weighing all of that is your prescriber’s job: if you’re wondering which one fits you, ask your doctor.

Frequently asked questions

Can I switch from Ozempic to Mounjaro?

That’s a medical decision. Neither the US Ozempic label nor the Mounjaro and Zepbound labels describe switching from one to the other or give dose equivalents^[1,4,5]. Tirzepatide starts at its own 2.5 mg starting dose^[4,5] in both labels. If you’re considering it, talk to your prescriber.

Is Zepbound the same as Mounjaro?

Same molecule, tirzepatide, and same maker, with the same 2.5 mg dose steps^[4,5]. They’re separate products with separate US labels: Mounjaro for type 2 diabetes (including children 10 and older), Zepbound for weight management and sleep apnea in adults^[4,5].

Is Mounjaro stronger than Ozempic?

For average weight loss, yes in the only head-to-head obesity trial, SURMOUNT-5: 20.2% on tirzepatide vs. 13.7% on semaglutide over 72 weeks^[15]. SURPASS-2 found larger HbA1c and weight drops than on Ozempic 1 mg^[17]. But both trials were open-label and Lilly-funded, and neither tested semaglutide 2 mg or 7.2 mg^[15,17]. “Stronger” doesn’t mean “better for you.”

Can you take Ozempic and Mounjaro together?

The labels advise against it. The Zepbound label says coadministration with other tirzepatide-containing products or with any GLP-1 receptor agonist is not recommended^[5]. The Wegovy label says the same about other semaglutide-containing products or any other GLP-1 receptor agonist^[2].

Which one costs less?

In the US, that depends on your insurance, so I don’t compare prices. In Spain and Mexico, an Ozempic pen costs less than a Mounjaro pen^{[26,29,30,31]}, but they aren’t interchangeable: different molecules, different doses and different approved uses.

Is Wegovy the same as Ozempic?

Same molecule, semaglutide, from the same maker, but at different doses and with different approved uses. Ozempic goes up to 2 mg a week, for type 2 diabetes^[1]. Wegovy injection’s recommended maintenance dose is 2.4 mg, for weight management, heart risk and MASH, and adults on it for weight can go up to 7.2 mg^[2].

What happens if you stop either one?

On average, much of the lost weight comes back. In the STEP 1 extension (study summary), a year after stopping semaglutide, people had regained about two-thirds of what they’d lost^[24]. In SURMOUNT-4 (trial summary), weight went back up by 14.0% over 52 weeks in people switched to placebo after 36 weeks on tirzepatide^[25]. I explain it in what happens when you stop Ozempic, Wegovy or Zepbound. Stopping or switching is a decision to make with your doctor.