What is Mounjaro, explained

What this guide covers

Mounjaro is tirzepatide, a once-weekly injection that acts on two gut hormones, GIP and GLP-1. What it is, who makes it, what it is approved for, and how it differs from Zepbound and the semaglutide drugs. This is patient education, not a substitute for the prescriber who knows your case. Generic names sit next to brand names throughout: semaglutide (Ozempic, Wegovy), tirzepatide (Mounjaro, Zepbound).

Key points

• The short answer. Mounjaro is the brand name for tirzepatide, a once-weekly injection made by Eli Lilly and FDA-approved for type 2 diabetes. What sets it apart from the semaglutide drugs (Ozempic, Wegovy) is that it activates two gut-hormone receptors instead of one: GIP and GLP-1. That is why it is called a dual agonist. The same molecule at the same doses is sold under a second brand name, Zepbound, for chronic weight management; Mounjaro and Zepbound are the same drug with different labels. If you reduce it to one sentence: Mounjaro is tirzepatide, a twincretin that copies two satiety-and-glucose hormones at once, which is the leading explanation for why its effects in trials tend to be large.
• Who makes Mounjaro, and what it is approved for. Mounjaro is made by Eli Lilly. The FDA approved it for improving blood sugar in adults with type 2 diabetes, alongside diet and exercise. It is not approved under the Mounjaro name for weight management, that indication belongs to its twin, Zepbound. This distinction matters in practice mostly for insurance and prescribing: a person with type 2 diabetes is typically prescribed Mounjaro, while a person being treated for obesity is prescribed Zepbound, even though the vial contents are identical. Your prescriber matches the brand to your diagnosis and what your plan covers.
• GIP plus GLP-1: what 'dual agonist' means. Most GLP-1 drugs copy a single gut hormone, GLP-1. Tirzepatide copies two: GIP (glucose-dependent insulinotropic polypeptide) as well as GLP-1. Both are incretin hormones your gut releases after eating, and both influence insulin and appetite, though GIP's role is still being mapped. The working theory from the trials is that hitting both receptors produces a larger combined effect on blood sugar and appetite than GLP-1 alone, which is the most-cited explanation for why tirzepatide's average results in head-to-head data came out ahead of semaglutide. The honest caveat is that the precise contribution of GIP is still an active research question, the dual mechanism is real, but the full biology is not fully settled.
• How it works in your body. Through those two receptors, Mounjaro does the familiar GLP-1 things plus the GIP layer: it reduces appetite by acting on the brain, slows how fast the stomach empties so you stay full longer, supports glucose-dependent insulin release, and suppresses glucagon (the hormone that raises blood sugar). The appetite effect is what most people notice, eating less without the constant effort, while the glucose effects are why it is a diabetes drug first. As with semaglutide, the slowed-stomach mechanism is also the direct cause of the nausea, burping, and constipation that show up, especially during dose increases. Same biology, same trade-offs.
• Dosing, as the label describes it. Mounjaro comes in several pen strengths and follows a fixed escalation, starting low and stepping up over months, not because higher is automatically better but to keep the gut side effects manageable. The lowest starting dose is meant to build tolerance rather than to treat, and each step up is where symptoms tend to flare briefly. The exact schedule and when to increase are your prescriber's decisions against your blood sugar and how you tolerate it; this page describes the shape of the ramp, not a personal prescription. The governing principle, true for every drug in this class, is that slow titration is what makes the drug livable. Our shared GLP-1 dosing schedule guide covers the general pattern.

Frequently asked questions