Comparisons

Zepbound vs Mounjaro

Published Sep 12, 2026 · 6 minute read

The same drug in the same pen at the same six doses. The label, the trials behind it, and the box are the only things that change.

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Key Takeaways

  • Identical molecule, identical six dose steps from 2.5 to 15 mg, identical pen. Only the label and the box differ.
  • Mounjaro was approved on diabetes trials (SURPASS). Zepbound was approved on obesity trials (SURMOUNT) and a sleep apnea trial.
  • In SURMOUNT-1, 15 mg produced 20.9% mean weight loss over 72 weeks; 57% of participants lost at least a fifth of their body weight.
  • In SURPASS-2, every tirzepatide dose beat semaglutide 1 mg on HbA1c, and 15 mg produced 5.5 kg more weight loss.
  • Zepbound is also sold in single-dose vials in the U.S. That is the one practical difference for the person injecting.
Mounjaro Zepbound
Molecule Tirzepatide Tirzepatide
Approved for Type 2 diabetes (adults and children 10+); cardiovascular risk reduction in type 2 diabetes Weight reduction; obstructive sleep apnea in adults with obesity
Dose steps 2.5, 5, 7.5, 10, 12.5, 15 mg weekly Identical
Device Single-dose pen Single-dose pen; single-dose vials in the U.S.
Pivotal trials SURPASS, SURPASS-CVOT SURMOUNT, SURMOUNT-OSA
Approved 2022 2023 (weight), 2024 (sleep apnea)

The trials behind each label

Each brand carries only the indications its own trial program tested. That is the entire reason two names exist.

Zepbound’s evidence is SURMOUNT. SURMOUNT-1 enrolled 2,539 adults with obesity and no diabetes for 72 weeks.

Weight reduction by tirzepatide dose, SURMOUNT-1Mean percent change from baseline at 72 weeks, adults with obesity and no diabetes, n=2,539
  • Tirzepatide
  • Placebo
5 mg
Tirzepatide
15%
Placebo
3.1%
10 mg
Tirzepatide
19.5%
Placebo
3.1%
15 mg
Tirzepatide
20.9%
Placebo
3.1%

Tirzepatide 5 mg 15.0%, 10 mg 19.5%, 15 mg 20.9%, placebo 3.1%. These are the Zepbound doses; the Mounjaro label uses the same strengths.

Source: Jastreboff 2022, N Engl J Med

57%of participants on 15 mg lost at least 20% of body weight in SURMOUNT-1, versus 3% on placebo.
−25.3events per hour: the change in apnea-hypopnea index at 52 weeks in SURMOUNT-OSA trial 1, versus −5.3 on placebo. Baseline was 51.5.
6.2%of the 15 mg group stopped for adverse events in SURMOUNT-1, versus 2.6% on placebo. Mostly gastrointestinal, mostly during escalation.

The sleep apnea indication came from SURMOUNT-OSA, two 52-week trials in adults with moderate to severe apnea and obesity. In people not using a PAP machine, AHI fell by 25.3 events per hour on tirzepatide versus 5.3 on placebo. In people already on PAP, it fell by 29.3 versus 5.5.

Mounjaro’s evidence is SURPASS. SURPASS-2 randomised 1,879 adults with type 2 diabetes to tirzepatide or semaglutide 1 mg for 40 weeks. Tirzepatide won at every dose.

HbA1c reduction by tirzepatide dose vs semaglutide 1 mg, SURPASS-2Mean change from baseline at 40 weeks in percentage points, adults with type 2 diabetes, n=1,879
  • Tirzepatide
  • Semaglutide 1 mg
5 mg
Tirzepatide
2.01 pp
Semaglutide 1 mg
1.86 pp
10 mg
Tirzepatide
2.24 pp
Semaglutide 1 mg
1.86 pp
15 mg
Tirzepatide
2.3 pp
Semaglutide 1 mg
1.86 pp

Tirzepatide 5 mg 2.01, 10 mg 2.24, 15 mg 2.30 percentage points; semaglutide 1 mg 1.86. This is the Mounjaro evidence base.

Source: Frías 2021, N Engl J Med

Weight loss in SURPASS-2 was 7.6, 9.3, and 11.2 kg on 5, 10, and 15 mg, against 5.7 kg on semaglutide. The cardiovascular indication came later from SURPASS-CVOT, where tirzepatide was non-inferior to dulaglutide, a drug already shown to cut cardiovascular events: 12.2% of patients had a major event versus 13.1%, hazard ratio 0.92.

Dose steps are identical

Step Dose, once weekly Minimum time before the next step
1 2.5 mg 4 weeks
2 5 mg 4 weeks
3 7.5 mg 4 weeks
4 10 mg 4 weeks; the Mounjaro ceiling for children 10 and older
5 12.5 mg 4 weeks
6 15 mg Adult ceiling on both labels

The ladder is transcribed from both labels and is the same on each. The sleep apnea indication specifies 10 or 15 mg as the maintenance dose. Both labels give the same missed-dose window: inject within four days, otherwise skip.

Pens versus vials

Mounjaro is a single-dose pen. Zepbound is the same pen, and in the U.S. also a single-dose vial at each strength, drawn with a syringe.

The vial changes three things for the person injecting. The dose is in milligrams on the prescription but drawn in millilitres on a syringe. A vial needs its own syringe and needle. And an opened vial has a discard date. The dose calculator does the millilitre conversion, and the inventory section of the tracking guide covers logging both formats.

Coverage follows the label

An insurer that covers Mounjaro for type 2 diabetes is covering the diabetes indication, not the molecule. The same plan can decline Zepbound, and the reverse. The brand on the prescription is therefore a coverage decision as much as a clinical one, and it is the prescriber’s decision, not the pharmacy’s.

What is identical

Everything in the safety sections. Both labels carry the boxed warning on thyroid C-cell tumors, the same contraindication for medullary thyroid carcinoma history or MEN 2, and the same warnings on pancreatitis, gallbladder disease, hypoglycemia with insulin or sulfonylureas, and severe gastrointestinal reactions.

Which comparison you wanted

The log entry is the same whichever brand is on the box: product, date, milligrams, site. How GLP-1 tracking works covers what to record.

7. Zepbound vs Mounjaro FAQ

  • Is Zepbound the same as Mounjaro?

    The drug is the same: tirzepatide, once weekly, in the same 2.5 to 15 mg steps and the same pen. The labels differ. Mounjaro is approved for type 2 diabetes and cardiovascular risk reduction in type 2 diabetes. Zepbound is approved for weight reduction and for obstructive sleep apnea in adults with obesity.

  • Why do two brands exist?

    Lilly ran separate trial programs for diabetes (SURPASS) and obesity (SURMOUNT) and filed separate applications. Novo Nordisk did the same with Ozempic and Wegovy. A separate brand lets each label carry only the indications its own trials support, and lets insurers cover one and not the other.

  • How much weight loss does tirzepatide produce?

    In SURMOUNT-1, adults with obesity and no diabetes lost 15.0%, 19.5%, and 20.9% of body weight on 5, 10, and 15 mg over 72 weeks, versus 3.1% on placebo. In SURPASS-2, adults with type 2 diabetes lost 7.6 to 11.2 kg over 40 weeks.

  • Does Zepbound come in a vial?

    Yes. In the U.S., Zepbound is supplied as a single-dose pen and as single-dose vials drawn with a syringe. Mounjaro is a pen only. The vial is the same drug at the same strengths.

  • Can Mounjaro be used for weight loss?

    Weight reduction is not on the Mounjaro label. Which product a prescriber chooses depends on diagnosis, the label, and coverage. This page reports the labels; it does not recommend a product.

8. Sources

References used for this article

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