What Is Mounjaro?

Summary: Mounjaro is the Eli Lilly brand name for tirzepatide, a once-weekly injection approved by the FDA in May 2022 for adults with type 2 diabetes, the same molecule sold as Zepbound for weight loss.

This content is for informational purposes only and is not medical advice. Always consult a qualified healthcare provider before starting, changing, or stopping any medication.

Mounjaro is Eli Lilly's brand name for tirzepatide, a once-weekly subcutaneous injection that the FDA approved on May 13, 2022 for adults with type 2 diabetes ^[3]. It is the first medication in a new drug class: a dual agonist that activates both the GIP and GLP-1 receptors in a single molecule. The same active ingredient is sold under a second brand, Zepbound, for chronic weight management. Mounjaro itself is not FDA-approved for weight loss, even though weight loss is a documented effect of the drug at every dose.

The rest of this page is the working knowledge you need: what it does in your body, who it is for, how it is dosed, how well it controls blood sugar in the trials that got it approved, what it costs, and the most common questions about how Mounjaro sits next to the other GLP-1 drugs on the market.

What Mounjaro is approved for

The FDA label for Mounjaro covers one indication: improving glycemic control in adults with type 2 diabetes mellitus, as an adjunct to diet and exercise ^[1]. That is the entire on-label use.

Mounjaro is not approved for:

• Weight loss alone. The same molecule was approved separately as Zepbound in November 2023 for chronic weight management in adults with obesity (BMI 30+) or overweight (BMI 27+) with at least one weight-related comorbidity ^[4]. If your goal is weight loss and you do not have diabetes, the on-label product is Zepbound, not Mounjaro.
• Type 1 diabetes. It has not been studied as a substitute for insulin in type 1 patients.
• Pediatric use under 10. Pediatric labeling for type 2 diabetes is limited and most prescribing is in adults.

The distinction between Mounjaro and Zepbound matters for insurance. The molecule is identical, the pen is identical, but the brand on the label determines whether your plan will cover it for your specific diagnosis.

What Mounjaro does to your body

Mounjaro is a dual GIP/GLP-1 receptor agonist. That phrase compresses three mechanisms working at once.

GLP-1 receptor activation. Glucagon-like peptide-1 is a gut hormone released after meals. When tirzepatide binds GLP-1 receptors on pancreatic beta cells, those cells release insulin in proportion to blood sugar. The "in proportion" part is why GLP-1 drugs rarely cause hypoglycemia on their own; the receptor only fires when glucose is already elevated. GLP-1 activation also suppresses glucagon (the hormone that tells your liver to release stored sugar), slows gastric emptying (food sits in the stomach longer, post-meal sugar spikes flatten out), and reduces appetite through receptors in the brainstem and hypothalamus.

GIP receptor activation. Glucose-dependent insulinotropic polypeptide is the other major incretin hormone. GIP amplifies insulin release in response to meals, influences fat metabolism in adipose tissue, and appears to modulate the nausea signal that GLP-1 activation alone produces. The GIP arm is what makes tirzepatide different from semaglutide (Ozempic, Wegovy), which is a pure GLP-1 agonist.

Combined effect. Acting on both receptors in one molecule produces stronger A1C reduction and stronger weight loss than activating GLP-1 alone, at least in the head-to-head trials Lilly ran ^[2]. The cost is a similar side effect profile to GLP-1 monotherapy: nausea, diarrhea, constipation, occasional vomiting, mostly during the dose escalation period.

Mounjaro is not an SGLT2 inhibitor (that is a different drug class, including empagliflozin and dapagliflozin, which work in the kidney). It is not an immunosuppressant. It is not a blood thinner. It does not contain exendin-4 (that is the synthetic GLP-1 analog inside exenatide, an older and chemically distinct drug). Tirzepatide is a 39-amino-acid synthetic peptide modeled on the native GIP sequence with modifications that let it bind both receptors and resist enzymatic breakdown.

Dosing: the 0.5 mL pen, weekly, titrated up

Mounjaro ships as a single-dose pre-filled pen at six strengths: 2.5 mg, 5 mg, 7.5 mg, 10 mg, 12.5 mg, and 15 mg, each containing 0.5 mL of solution ^[1][5]. There is also a KwikPen (four doses per pen) and a multi-dose vial format at 0.6 mL per dose.

The injection is once weekly, subcutaneous, into the abdomen, thigh, or upper arm. There is no dial. You attach the needle, press the button, count to ten, and withdraw.

The titration schedule is fixed by the FDA label:

Patients stop titrating once their A1C target is met or once they hit a dose that is well tolerated. The 2.5 mg starting dose exists specifically to let the gut adapt to slowed gastric emptying. Skipping ahead is the most reliable way to get knocked out by nausea and abandon the drug. The same titration schedule applies to Zepbound for weight loss.

How well Mounjaro works for type 2 diabetes

The pivotal data come from the SURPASS clinical trial program, five global phase 3 trials that compared tirzepatide to placebo, basal insulin, and semaglutide across more than 6,000 adults with type 2 diabetes.

The most cited trial is SURPASS-2, a 40-week, open-label, head-to-head against semaglutide 1 mg, the highest semaglutide dose approved for diabetes at the time ^[2]. Results at week 40:

Tirzepatide produced a larger A1C drop at every dose, and the 15 mg arm cut A1C by an average of 2.3 percentage points from a baseline near 8.3% ^[2]. For perspective, the diabetes outcomes literature treats a 1.0-point A1C reduction as clinically meaningful. SURPASS-2 saw more than twice that at the top dose.

Across the SURPASS program more broadly, roughly 80% to 97% of tirzepatide-treated patients reached an A1C below 7.0%, and a majority reached below 5.7% (the technical "non-diabetic" range). Those are not weight loss numbers; those are blood sugar numbers. The weight loss in SURPASS was a secondary endpoint, and it consistently exceeded what GLP-1 monotherapy produced.

Side effects

The Mounjaro side effect profile is the standard GLP-1 / GIP profile, dominated by gastrointestinal events that cluster during the titration weeks and fade with continued use.

Most common (incidence above 5%) per the FDA label ^[1]:

• Nausea (up to 18% at 5 mg, higher at 15 mg)
• Diarrhea (up to 17%)
• Decreased appetite (up to 11%)
• Vomiting (up to 13%)
• Constipation (up to 9%)
• Dyspepsia (indigestion)
• Abdominal pain
• Injection site reactions

Less common but serious:

• Pancreatitis. Mounjaro carries a warning for acute pancreatitis. Patients are told to stop the drug and seek care for severe, persistent abdominal pain.
• Hypoglycemia. Rare on Mounjaro monotherapy. Common if Mounjaro is combined with insulin or a sulfonylurea, which is why doses of those drugs are often reduced when Mounjaro is started.
• Acute kidney injury. Usually secondary to dehydration from vomiting or diarrhea.
• Gallbladder disease. Cholecystitis and cholelithiasis show up at higher rates than placebo.
• Diabetic retinopathy worsening. Documented in patients with pre-existing retinopathy; rapid A1C improvement can transiently worsen eye disease.

Boxed warning: thyroid C-cell tumors. In rat studies, tirzepatide caused thyroid C-cell tumors. Whether this translates to humans is unknown. The boxed warning contraindicates Mounjaro in anyone with a personal or family history of medullary thyroid carcinoma (MTC) or multiple endocrine neoplasia syndrome type 2 (MEN 2) ^[1].

Most patients who tolerate the titration phase tolerate the maintenance dose indefinitely. The drop-out rate in SURPASS-2 due to adverse events was roughly 6% to 8% across tirzepatide arms, comparable to semaglutide.

What Mounjaro costs

The 2026 list price for a one-month supply of Mounjaro is approximately $1,069.08 for any of the six dose strengths. List price applies to cash payers without coverage and is the published wholesale acquisition cost in the US.

What you actually pay depends on insurance:

• Commercial insurance covering Mounjaro for type 2 diabetes. With the Lilly Mounjaro Savings Card, eligible commercially-insured patients with type 2 diabetes can pay as little as $25 per fill for up to a 3-month supply, capped at a maximum savings amount per year. The savings card is for type 2 diabetes only and is restricted by Lilly's terms.
• Commercial insurance with no Mounjaro coverage. The savings card offers a lower maximum benefit for off-formulary fills, and the out-of-pocket cost can still run several hundred dollars per month.
• Medicare or Medicaid. Savings card excluded. Pricing follows the Part D benefit; many Medicare beneficiaries pay between $50 and $300 per month after deductible, depending on the plan tier.
• Cash pay, no insurance, no savings card. Full list price, roughly $1,069 per 28-day supply.
• Lilly Direct self-pay vial program. Lilly sells Zepbound (not Mounjaro) single-dose vials directly to self-pay patients at reduced prices (the 2.5 mg vial at around $349 per month and the 5 mg at around $499 as of recent updates). The vial format is not available for Mounjaro; that program is Zepbound-only.

Insurance coverage for Mounjaro for the on-label diabetes indication is broad. Coverage for off-label weight loss use is rare and usually requires a separate Zepbound prescription anyway.

Who Mounjaro is for

Mounjaro is for adults with type 2 diabetes who need better glycemic control than diet, exercise, and (often) metformin alone are giving them. Common patient profiles where prescribers reach for Mounjaro:

• A1C above 7.5% on metformin alone or on metformin plus an SGLT2 inhibitor. Mounjaro is added to bring A1C below 7.0%.
• Type 2 diabetes with overweight or obesity. The dual benefit (A1C reduction plus 5 to 11 kg of weight loss on average) makes Mounjaro a preferred add-on over basal insulin in this group, since insulin tends to cause weight gain.
• Patients who failed semaglutide. Either due to insufficient A1C response or due to plateauing weight loss. The SURPASS-2 head-to-head supports tirzepatide as the more potent option.
• Patients seeking once-weekly dosing. Daily oral diabetes pills come with adherence problems. A once-weekly injection is easier to remember and harder to skip.

Mounjaro is not appropriate for:

• Type 1 diabetes
• History of medullary thyroid carcinoma or MEN 2 (boxed warning)
• History of severe gastroparesis or recurrent pancreatitis
• Pregnancy or planned pregnancy (limited human data; the drug is washed out before conception by current guidance)
• Children under 10 (no labeled use; pediatric expansion is limited)

The decision is between you and a prescriber who has reviewed your full medical history. The list above is the standard screening pass.

Mounjaro vs the other GLP-1 brands

For context, here is how Mounjaro sits next to the other major incretin-class brands.

The split between diabetes brand and weight management brand (Mounjaro/Zepbound, Ozempic/Wegovy, Victoza/Saxenda) is a regulatory and commercial convention. The molecule is the same within each pair. The differences are FDA-labeled indication, available dose strengths, packaging, and which savings programs apply.

Common questions about Mounjaro

What is Mounjaro used for?

Mounjaro is FDA-approved for type 2 diabetes in adults, to lower blood sugar alongside diet and exercise. It is not approved for weight loss; the same molecule sold as Zepbound is the on-label weight loss product.

Is Mounjaro a GLP-1?

Mounjaro activates the GLP-1 receptor, but it also activates the GIP receptor. It is technically a dual GIP/GLP-1 receptor agonist, the only drug in that class on the US market as of 2026.

Is Mounjaro the same as Ozempic?

No. Ozempic is semaglutide, a single GLP-1 receptor agonist. Mounjaro is tirzepatide, which hits both GIP and GLP-1. In the SURPASS-2 head-to-head, Mounjaro produced larger A1C reductions and larger weight loss.

Is Mounjaro an SGLT2 inhibitor?

No. SGLT2 inhibitors (empagliflozin, dapagliflozin, canagliflozin) work in the kidney to spill glucose into urine. Mounjaro works through gut hormone receptors on the pancreas and brain.

Is Mounjaro an immunosuppressant?

No. Mounjaro does not suppress the immune system. It is a synthetic peptide that binds GIP and GLP-1 receptors. It has no documented effect on immune cell function.

Is Mounjaro a blood thinner?

No. Mounjaro has no anticoagulant activity. It does not affect platelet function or clotting factors and is not used to prevent stroke or clots.

Does Mounjaro contain exendin-4?

No. Exendin-4 is the active ingredient in exenatide (Byetta, Bydureon), a different and older GLP-1 drug derived from Gila monster venom. Tirzepatide is a 39-amino-acid synthetic peptide engineered separately and modeled on native GIP.

What does Mounjaro do to your body?

It triggers insulin release when blood sugar rises, suppresses glucagon, slows gastric emptying, and reduces appetite by acting on brain receptors. The net effect is lower blood sugar and reduced food intake.

How much weight do people lose on Mounjaro?

In SURPASS-2 (type 2 diabetes), the 15 mg dose produced an average weight loss of 11.2 kg over 40 weeks. In SURMOUNT-1 (the Zepbound obesity trial), people without diabetes lost an average of about 20% of body weight at the 15 mg dose over 72 weeks.

How much does Mounjaro cost without insurance?

List price is approximately $1,069 per 28-day supply in the US for any pen strength. With the Lilly savings card and commercial insurance covering Mounjaro for type 2 diabetes, eligible patients pay as little as $25 per fill.

When was Mounjaro approved?

The FDA approved Mounjaro on May 13, 2022, for adults with type 2 diabetes. Zepbound (the same molecule for weight management) followed in November 2023.

Can you use Mounjaro for weight loss if you do not have diabetes?

Not on label. Insurance covering Mounjaro for diabetes will not cover it for off-label weight use. The on-label weight loss product is Zepbound, which contains the same molecule. Ask your prescriber about Zepbound if weight management is the goal.

The short version

Mounjaro is Eli Lilly's tirzepatide pen, approved by the FDA in May 2022 for adults with type 2 diabetes. One molecule, two FDA brands (Mounjaro for diabetes, Zepbound for weight management), one weekly injection at 0.5 mL per dose, six strengths from 2.5 mg to 15 mg, list price around $1,069 per month before any savings program. The mechanism is dual GIP/GLP-1 receptor activation, which in the SURPASS-2 trial dropped A1C by 2.3 percentage points at the maximum dose and produced larger weight loss than semaglutide 1 mg head-to-head. The side effects are GI-dominated and cluster during titration. If you have type 2 diabetes and your A1C is not where you want it, Mounjaro is one of the most effective injectable options on the US market.