Mounjaro vs Semaglutide: Head-to-Head Comparison (2026)

Mounjaro vs Semaglutide: Quick Comparison Table

The SURMOUNT-5 figures come from one randomized trial in adults with obesity (no type 2 diabetes), funded by Eli Lilly. Trial populations, durations, and designs differ across studies, so single-arm numbers from separate trials should not be read as a direct contest.

How Each Drug Works

Both medications copy natural gut hormones to reduce appetite and improve blood sugar control. The difference is how many hormone pathways each one engages. For a deeper molecular breakdown beyond the brand names, see our tirzepatide vs semaglutide analysis.

Semaglutide is a GLP-1 receptor agonist. It slows gastric emptying, reduces appetite, and stimulates insulin release when blood sugar rises. Tirzepatide does all of that through the GLP-1 pathway and adds a second target, the GIP receptor, which may enhance insulin sensitivity and affect fat metabolism. Neither is taken as a pill in this comparison. Both Mounjaro and Wegovy are subcutaneous injections. Oral semaglutide tablets exist (the Ozempic pill for type 2 diabetes, which reformulated and renamed Rybelsus in 2026, and the Wegovy pill for weight management) but are not the subject here.

What Is Mounjaro (Tirzepatide)?

What Is Semaglutide (Ozempic and Wegovy)?

Clinical Trial Evidence: Mounjaro vs Semaglutide

The numbers below are real, but each one comes from a different trial with its own population and design. That changes how to read them.

SURMOUNT-5: The Only Head-to-Head Obesity Trial (2025)

SURMOUNT-5 randomized 751 adults with obesity (no type 2 diabetes) to tirzepatide or semaglutide for 72 weeks, with both arms titrated to the maximum doses approved at the time (tirzepatide 15 mg, semaglutide 2.4 mg). Participants on tirzepatide lost an average of 20.2% of body weight versus 13.7% on semaglutide, a difference of roughly 6.5 percentage points (around 17 lbs for a typical participant). 31.6% of the tirzepatide group lost 25% or more of their body weight, compared with 16.1% of the semaglutide group.

SURPASS-2: The Type 2 Diabetes Head-to-Head (2021)

SURPASS-2 randomized 1,879 adults with type 2 diabetes over 40 weeks, comparing tirzepatide 5 mg, 10 mg, and 15 mg against semaglutide 1.0 mg once weekly. Note that the semaglutide dose here was the 1.0 mg type 2 diabetes dose, not the 2.4 mg Wegovy weight loss dose, so the weight comparison is not a Wegovy comparison. The published trial reports treatment differences in kilograms rather than absolute percent loss per arm:

• Tirzepatide 5 mg: 1.9 kg more weight reduction than semaglutide 1.0 mg
• Tirzepatide 10 mg: 3.6 kg more weight reduction than semaglutide 1.0 mg
• Tirzepatide 15 mg: 5.5 kg more weight reduction than semaglutide 1.0 mg

For blood sugar control, HbA1c fell by 2.30 percentage points on tirzepatide 15 mg and 1.86 percentage points on semaglutide 1.0 mg over the same period.

Single-Arm Trial Context

These trials enrolled different populations over different durations, so a direct comparison is not appropriate. They do provide realistic expectations for each drug individually. In SURMOUNT-1, tirzepatide 15 mg produced 20.9% mean body weight loss at 72 weeks. In STEP 1, semaglutide 2.4 mg produced 14.9% mean body weight loss at 68 weeks. Both trials combined the medication with diet and exercise support.

Weight Loss Differences: What the Numbers Mean in Practice

Here is what those trial averages work out to for a person who weighs 220 lbs (100 kg). These are averages from maximum doses combined with a diet and exercise protocol, not a promise of individual results.

Individual results vary widely. Many people in the real world stop titrating before the maximum dose, plateau earlier, or stop for cost or tolerability reasons. The trial averages are a ceiling reference, not a forecast for any one person.

Side Effects: What to Expect on Each

Because both drugs activate GLP-1 receptors, they share the same core gastrointestinal side effect profile.

Shared Side Effects

Nausea, diarrhea, constipation, and vomiting are the most common side effects for both medications. They tend to be worst during dose escalation and usually settle once a dose level stabilizes. Both carry the same FDA boxed warning for thyroid C-cell tumors based on rodent studies. Both are contraindicated in people with a personal or family history of medullary thyroid carcinoma or multiple endocrine neoplasia syndrome type 2. This is stated as a precaution on the label; it is not a finding that the drugs cause thyroid cancer in humans.

Tolerability Differences

Tirzepatide may carry somewhat higher gastrointestinal event rates at equivalent steps, possibly because the GIP pathway affects gut motility differently. The overall picture stays similar between the two, and SURMOUNT-5 reported broadly comparable safety profiles across both arms. For most people, escalation pace and individual sensitivity matter more than which molecule it is.

Muscle Loss Consideration

Early data has raised the question of whether tirzepatide preserves more lean mass than semaglutide, possibly linked to the GIP pathway. This is preliminary and is not an established FDA-label claim for either drug. With either medication, resistance training and adequate protein intake are commonly recommended to limit muscle loss during rapid weight reduction.

FDA Indications and Who Can Take Each

Getting the brand-indication mapping right is what most comparisons get wrong. Here it is, brand by brand.

Tirzepatide (Mounjaro and Zepbound)

• Mounjaro: type 2 diabetes in adults and children 10 and older (first FDA-approved May 2022), and reducing the risk of major cardiovascular events in adults with type 2 diabetes at high cardiovascular risk^[9]
• Zepbound: chronic weight management in adults with obesity, or overweight with a weight-related condition (2023)
• Zepbound: moderate-to-severe obstructive sleep apnea in adults with obesity (2024)

Semaglutide (Ozempic and Wegovy)

• Ozempic: type 2 diabetes in adults (FDA-approved 2017), reducing the risk of major cardiovascular events in adults with type 2 diabetes and established cardiovascular disease, and reducing kidney-disease and cardiovascular-death risk in adults with type 2 diabetes and chronic kidney disease^[10]
• Wegovy: chronic weight management in adults (2021) and in pediatric patients aged 12 and older (December 2022)
• Wegovy: reducing the risk of cardiovascular death, non-fatal heart attack, and non-fatal stroke in adults with cardiovascular disease and a BMI of 27 or higher (2024, based on the SELECT trial^[8])
• Wegovy: noncirrhotic MASH (metabolic dysfunction-associated steatohepatitis) with moderate to advanced liver fibrosis in adults (August 2025, accelerated approval)^[11]

Dosing and Titration Compared

Both medications are once-weekly subcutaneous injections that the patient self-administers, and both use a gradual dose escalation to limit side effects.

• Tirzepatide: starts at 2.5 mg, titrating every 4 weeks through 5, 7.5, 10, 12.5, up to a maximum of 15 mg (seven dose levels)
• Semaglutide (Wegovy): starts at 0.25 mg, titrating every 4 weeks through 0.5, 1.0, 1.7, up to the recommended 2.4 mg maintenance dose (five dose levels); a 7.2 mg maximum is available after at least 4 weeks tolerating 2.4 mg

The escalation schedule can be adjusted by a prescriber based on tolerability. Slower titration is common when side effects are pronounced. GLP3Planner has free calculators for both molecules so you can map your own schedule.

Which Drug Might Be Right for You?

This is a way to frame the question, not a recommendation. Use it to shape the conversation with whoever writes your prescription.

• Indication: For type 2 diabetes, both Mounjaro and Ozempic are approved options. For weight management without diabetes, the relevant brands are Zepbound and Wegovy.
• Prior response: If weight loss has plateaued on semaglutide, some people see additional loss after switching to tirzepatide. See switching from Ozempic to Mounjaro for how that transition is typically handled.
• Cardiovascular history: Wegovy has an FDA-approved cardiovascular risk reduction indication for adults with cardiovascular disease and overweight or obesity; Zepbound does not. Mounjaro and Ozempic both carry cardiovascular risk reduction indications, but only for adults with type 2 diabetes^[9][10].
• Pediatric patients: For weight management, only Wegovy is approved for patients aged 12 and older; Zepbound is for adults. For type 2 diabetes, Mounjaro is approved from age 10^[9].
• Sleep apnea: Only Zepbound carries the obstructive sleep apnea indication.

Your prescriber is the only person who can assess which option fits your health history, insurance, and goals. Cost is similar enough between the two that it is rarely the deciding factor on its own; insurance coverage usually is.

Pharmacokinetics: Half-Life and Dose Timing

Half-life is where these two drugs actually differ, and it is what GLP3Planner exists to model.

• Tirzepatide half-life: approximately 5 days, reaching steady state in about 4 weeks of consistent weekly dosing (Mounjaro label)^[9]
• Semaglutide half-life: approximately 7 days, reaching steady state in roughly 4 to 5 weeks (Ozempic label)^[10]

Semaglutide's longer half-life means it stays in the system slightly longer if a dose is missed; tirzepatide clears a little faster. In practice, both are forgiving with a one-day shift in injection timing because both have long half-lives relative to the weekly schedule. A calculator that models exponential decay makes the accumulation pattern easy to see.

Watch: An Endocrinologist on the SURMOUNT-5 Head-to-Head Trial

Dr Jawad Bashir, an endocrinology and diabetes specialist, walks through the SURMOUNT-5 trial comparing tirzepatide and semaglutide for weight loss.