Mounjaro vs Ozempic: Comparing Two GLP-1 Medications

Mounjaro and Ozempic are the two most recognized injectable medications in the GLP-1 class. Both are prescribed frequently for weight loss, but neither is actually FDA-approved for that purpose. Mounjaro is approved for type 2 diabetes. So is Ozempic. The weight loss versions are Zepbound (tirzepatide) and Wegovy (semaglutide). This distinction matters for insurance coverage, prescribing, and what clinical data applies. This page compares the two diabetes brands and their weight-loss counterparts on mechanism, trial results, side effects, and cost.

Quick Comparison Table

When people say "I'm on Mounjaro for weight loss," they are using a diabetes drug off-label. Zepbound is the weight management version. When people say "I'm on Ozempic to lose weight," they are also off-label. Wegovy is the semaglutide product approved for weight management, at a higher maximum dose (2.4 mg vs 2 mg). Insurance coverage, copay card eligibility, and label-supported claims all depend on which product is actually prescribed.

Weight Loss Comparison

The SURMOUNT-5 trial directly compared tirzepatide and semaglutide in a head-to-head design. Both arms were titrated to the maximum tolerated dose over 72 weeks (PMID 40353578).

Mounjaro Weight Loss Data

Tirzepatide's weight loss data comes from the SURMOUNT program. In SURMOUNT-1, the 15 mg dose produced a mean weight loss of 20.9% at 72 weeks in adults with obesity but without diabetes (PMID 35658024). The 10 mg dose achieved 19.5%, and the 5 mg dose achieved 15.0%. Placebo was 3.1%. These are the numbers for the brand-name molecule that Mounjaro contains.

In SURMOUNT-5, tirzepatide at maximum tolerated dose produced 20.2% weight loss over 72 weeks, consistent with SURMOUNT-1.

Ozempic Weight Loss Data

Semaglutide's weight loss data comes primarily from the STEP trial program. In STEP 1, semaglutide 2.4 mg (the Wegovy dose, not the Ozempic dose) produced approximately 14.9% weight loss at 68 weeks. Ozempic's maximum dose is 2 mg, which is lower than the Wegovy dose, so weight loss on Ozempic specifically may be slightly less than what STEP 1 reported.

In SURMOUNT-5, semaglutide at maximum tolerated dose produced 13.7% weight loss at 72 weeks. That is 6.5 percentage points less than tirzepatide in the same trial. The difference was statistically significant.

For a 220-pound patient, the difference between 13.7% and 20.2% is roughly 14 pounds. That is not trivial over the same treatment duration with the same injection schedule. Tirzepatide's dual receptor mechanism appears to deliver a meaningful efficacy advantage over semaglutide's single-receptor approach. Our full tirzepatide vs semaglutide comparison covers additional data points and switching considerations.

Side Effect Comparison

Both drugs cause gastrointestinal adverse events at high rates. Slowed gastric emptying reduces appetite but also produces nausea, diarrhea, and vomiting in a significant fraction of patients. The types of side effects are nearly identical. The frequencies differ modestly.

Semaglutide shows higher reported rates for all four major GI side effects in the label data. Both drugs carry boxed warnings for thyroid C-cell tumors. Both are contraindicated in patients with medullary thyroid carcinoma or MEN2. Both list pancreatitis and gallbladder events as serious risks. The safety profiles are more alike than different. For a detailed breakdown of tirzepatide's side effects, see our side effects page.

Cost Comparison

At list price, Mounjaro and Ozempic are within $50 of each other per month. The weight loss brands are more expensive: Zepbound lists at $1,499 and Wegovy at $1,849. Insurance coverage determines the actual out-of-pocket number for brand-name products. For patients paying cash, compounded versions from providers like BiltRx offer a dramatic cost reduction. Compounded tirzepatide runs $129 per month. Compounded semaglutide runs $81 per month. Neither compounded product is FDA-approved.

The cost question often comes down to insurance formulary placement. Plans that cover Mounjaro for T2D may not cover Zepbound for weight loss. Plans that cover Ozempic may not cover Wegovy. Patients without T2D who want either drug for weight management frequently face denials and end up paying cash or choosing compounded versions. Our tirzepatide cost breakdown covers this in more detail.

Which One Is Right for You?

The trial data gives tirzepatide a clear edge on weight loss efficacy. A 6.5 percentage point advantage in a head-to-head trial is substantial. For patients whose primary goal is maximum weight reduction and who can access either drug, tirzepatide has the stronger evidence.

Semaglutide has a longer track record. It has been on the market since 2017, and the SELECT trial showed reduced major cardiovascular events in patients with obesity and established heart disease. Tirzepatide does not yet have published cardiovascular outcomes data from its obesity trials. For patients with cardiovascular disease, this may be a deciding factor.

Cost may override everything else. If your insurance covers one but not the other, that makes the decision for you. If you are paying cash for compounded options, semaglutide at $81 per month is $48 cheaper than tirzepatide at $129. Whether the additional weight loss justifies the extra $576 per year depends on individual priorities.