Zepbound vs. Mounjaro: one molecule, two labels, compared line by line

Both pens and vials hold the same tirzepatide at 2.5, 5, 7.5, 10, 12.5 or 15 mg, and both come as a four-dose KwikPen. What changes is the approved use, and with it who can take the drug and at what dose.

Mounjaro is approved to improve blood sugar control in adults and children aged 10 and older with type 2 diabetes. It is also approved to lower the risk of heart attack, stroke and cardiovascular death in adults with type 2 diabetes at high risk. Adults can go to 15 mg; children stop at 10 mg.

Zepbound is approved for adults with obesity, or with overweight plus a weight-related condition. Maintenance is 5, 10 or 15 mg. For moderate to severe obstructive sleep apnea with obesity, the maintenance dose is 10 or 15 mg. Zepbound is adult-only.

No trial compares Zepbound with Mounjaro, because the drug inside is the same. Each label rests on its own trial program.

Mounjaro's diabetes evidence (SURPASS). In SURPASS-2, tirzepatide lowered HbA1c by 2.01 to 2.30 points over 40 weeks, more than semaglutide 1 mg. Weight fell too, but as a secondary result: the 15 mg group lost 5.5 kg more than the semaglutide group. SURPASS-CVOT compared tirzepatide with dulaglutide in 13,299 adults with type 2 diabetes and established heart disease, with a mean age of 64 and a median follow-up of about 4 years. Major cardiac events occurred in 12.2% versus 13.1% (hazard ratio 0.92), which met noninferiority. The FDA added the heart indication on August 28, 2026.

Zepbound's weight and sleep evidence (SURMOUNT). SURMOUNT-1 reported average losses of 15.0%, 19.5% and 20.9% at 5, 10 and 15 mg over 72 weeks, against 3.1% on placebo. SURMOUNT-4 showed that people who stayed on tirzepatide after 36 weeks lost a further 5.5%, while those switched to placebo regained 14%. Two 52-week sleep apnea trials, one with and one without CPAP-type therapy, showed larger drops in breathing interruptions than placebo. SURMOUNT-5 later beat semaglutide 2.4 mg for weight, 20.2% versus 13.7%.

Same molecule, so the same side-effect profile. The labels word it slightly differently because they were built from different patient groups.

Mounjaro lists nausea, diarrhea, decreased appetite, vomiting, constipation, indigestion and belly pain as its most common reactions. Zepbound's weight trials put nausea at 25% to 29% and diarrhea at 19% to 23%, against 8% each on placebo. Injection-site reactions, tiredness, hair loss and reflux also appear.

The practical difference is who is taking it. Many Mounjaro users also take insulin or a sulfonylurea, which raises the chance of low blood sugar, so those doses are often lowered. Both labels also warn about diabetic retinopathy getting worse in people with a history of it. Both warn about pancreatitis, gallbladder disease and reduced birth-control pill absorption after dose changes. Both carry the rodent thyroid C-cell boxed warning.

Your diagnosis decides this more than preference does.

Mounjaro is the label that fits if you have type 2 diabetes, especially with heart disease or high cardiovascular risk, since it now carries that indication. It is also the only tirzepatide option for a child aged 10 or older with type 2 diabetes.

Zepbound is the label that fits if the reason for treatment is obesity, overweight with a related condition, or obstructive sleep apnea with obesity. Mounjaro used only for weight is off-label, and insurers often deny it.

If you have both diabetes and obesity, either label can apply. The choice usually follows which condition your plan covers, and your prescriber can advise.

Neither fits with a personal or family history of medullary thyroid carcinoma or MEN2, a past serious reaction to tirzepatide, or pregnancy. Compounded tirzepatide is neither Mounjaro nor Zepbound and is not FDA-approved. At Temi it starts at $104.99 per 8.5 mg vial plus a $39 service fee [usetemi.com/medications/compounded-tirzepatide-injectable, verified Sep 28, 2026].