Zepbound and Mounjaro are the same medicine sold under two names. Both are weekly tirzepatide injections from Eli Lilly, and both come in the same strengths. FDA approved Mounjaro first, in May 2022, for type 2 diabetes. Zepbound followed in November 2023 for weight management [3] [4]. The tirzepatide guide covers how the drug works; this page covers what actually differs between the two boxes.
Same drug, same maker, same strengths
Tirzepatide acts on two gut-hormone receptors, GIP and GLP-1, which lowers blood sugar and appetite. Both labels list the same strengths, from 2.5 mg to 15 mg, in the same four device types: single-dose pens, single-dose vials, multi-dose vials and KwikPens [1] [2]. Both labels start at 2.5 mg once a week, which is a starting dose only, and both allow up to 15 mg a week in adults.
What each one is approved for
| Zepbound | Mounjaro | |
|---|---|---|
| Active ingredient | Tirzepatide | Tirzepatide |
| Maker | Eli Lilly | Eli Lilly |
| Approved for | Weight management in adults with obesity, or overweight plus a weight-related condition; moderate to severe sleep apnea in adults with obesity | Blood sugar control in type 2 diabetes; cutting heart-attack and stroke risk in adults with type 2 diabetes at high risk |
| First approval | November 8, 2023 | May 13, 2022 |
| Later approvals | Sleep apnea, December 20, 2024 | Children 10 and older, December 19, 2025; heart-risk reduction, August 27, 2026 |
| Ages | Adults only | Adults and children 10 and older |
| Devices | Single-dose pen or vial, multi-dose vial, KwikPen | Single-dose pen or vial, multi-dose vial, KwikPen |
| Self-pay (LillyDirect) | $299 to $449 a month with on-time refills | $499 a month at every strength |
| What insurance looks at | A weight or sleep apnea diagnosis; many plans exclude weight drugs | A type 2 diabetes diagnosis |
Indications and devices from the Zepbound [1] and Mounjaro [2] labels; dates from Drugs@FDA [3] [4] and FDA [5]; prices from LillyDirect [6] [7].
Mounjaro's newest indication is the one people ask about most. In SURPASS-CVOT, about 13,000 adults with type 2 diabetes and heart disease took tirzepatide or dulaglutide (Trulicity), an older GLP-1 drug. Heart attacks, strokes and heart deaths occurred in 12.2% and 13.1%, which met the bar for being no worse than dulaglutide but didn't prove it better [11]. Eli Lilly funded the trial. Zepbound's label now includes those trial data too, but as information, not a heart-risk indication.
Is Zepbound better than Mounjaro for weight loss? It's the same drug
The weight numbers differ because the people in the trials differed. Zepbound's main trial, SURMOUNT-1, enrolled 2,539 adults with obesity and no diabetes. At the top dose, they lost 20.9% of their body weight on average over 72 weeks, against 3.1% on placebo [9].
SURMOUNT-2 used the same drug in 938 adults with obesity and type 2 diabetes. Average weight loss at 72 weeks was 12.8% and 14.7% at the two doses tested, against 3.2% on placebo [10]. Lilly funded both trials. So the same drug produced less weight loss in people with diabetes, a pattern seen across GLP-1 drugs.
In practice, that means two people taking the same dose will get the same drug whichever box it comes in. If you have type 2 diabetes, expect results closer to SURMOUNT-2 than SURMOUNT-1, on either brand. If you're comparing tirzepatide with the other weight-loss shot, the Zepbound vs Wegovy comparison covers the one head-to-head trial.
Side effects are the same drug's, measured in different groups
Both labels carry the same boxed warning about thyroid C-cell tumors seen in rodents, and the same warnings about pancreatitis, gallbladder disease, kidney injury from dehydration and severe digestive reactions [1] [2]. The digestive numbers look different on paper because they were measured in different people.
- Zepbound label (weight trials): digestive side effects in 56% of people at each dose, against 30% on placebo [1].
- Mounjaro label (diabetes trials): digestive side effects in 37.1% to 43.6% by dose, against 20.4% on placebo [2].
- Both labels: most nausea, vomiting and diarrhea happened while the dose was being raised and eased over time.
Low blood sugar is the one risk that shifts with your situation rather than the brand. It's more likely if you also take insulin or a sulfonylurea for diabetes, which is why the diabetes setting changes what your prescriber watches. The Mounjaro safety guide covers this in more depth.
Zepbound costs less in cash; coverage depends on your diagnosis
This is where the two brands really split. Lilly sells both through LillyDirect, and the cash prices don't match, even at the same strength.
| Strength | Zepbound (vial or KwikPen) | Mounjaro |
|---|---|---|
| 2.5 mg (starting dose) | $299 | $499 |
| 5 mg | $399 | $499 |
| 7.5 mg | $449 with a refill within 45 days (otherwise $499) | $499 |
| 10 mg, 12.5 mg, 15 mg | $449 with a refill within 45 days (otherwise $699) | $499 |
Monthly prices from LillyDirect [6] [7]. Zepbound vials need a separate needle and syringe purchase; KwikPens need pen needles.
So Zepbound is $200 cheaper at the starting dose and $50 cheaper at the higher doses, as long as you refill on time. Miss the 45-day window on a high dose and Zepbound costs more than Mounjaro. Lilly doesn't say why the two brands are priced differently.
Insurance follows the label. Plans that cover diabetes drugs usually cover Mounjaro for type 2 diabetes. Coverage for weight-loss drugs like Zepbound varies by plan, and many plans exclude them. For people on Medicare, Lilly says eligible Part D members can get Zepbound for weight management for no more than $50 a month through the Medicare GLP-1 Bridge [8]; CMS sets who qualifies. The Zepbound cost guide covers savings cards and coverage in more depth, and the monthly cost calculator works out your monthly total.
Can you switch between them? Your prescriber decides
Because it's the same molecule at the same strengths, a change from one brand to the other is usually about coverage or diagnosis, not about a different drug. That decision belongs to your prescriber and, often, your insurer. Don't take both: Zepbound's label says using it with other tirzepatide products or with any GLP-1 drug "is not recommended" [1].
If you're weighing a compounded version against the brands, the compounded tirzepatide vs Zepbound guide explains what's different. For the diabetes side of the choice, see the Ozempic vs Mounjaro comparison, and for each brand on its own, the Zepbound guide and Mounjaro guide.