Here's what we'll cover
Here's what we'll cover
Wegovy (semaglutide) and Mounjaro (tirzepatide) are both injectable medications prescribed for weight management, but that sentence is only fully accurate if you are in the United Kingdom. In the United States, Mounjaro is approved exclusively for Type 2 diabetes. The same molecule, tirzepatide, is sold as Zepbound for weight management in the US.
This means most of the top ranking content for this search is written from a UK perspective and gives US readers materially misleading guidance about what they can actually be prescribed.
The Problem With Almost Every Page Ranking for This Search
The top results for this comparison are dominated by UK sources. British Heart Foundation, ASDA Online Doctor, Chemist 4 U, and PrivateDoc all rank in the top positions. Their content is accurate for the UK, where Mounjaro is indeed a weight loss drug.
But a US reader landing on those pages will get a fundamentally wrong picture of what they can walk into a doctor's office and be prescribed. In the United States, asking your physician for Mounjaro for weight loss is asking for an off label use of a diabetes medication. The on label weight loss product containing the same molecule is Zepbound.
This is not a technicality. It affects insurance coverage, prescribing, and whether your pharmacist fills the prescription at all. Understanding which comparison actually applies to your country is the starting point for everything else on this page.
What Each Drug Is Actually Approved For
In the United States
Wegovy (semaglutide, Novo Nordisk) is FDA approved for:
- Chronic weight management in adults with obesity or overweight with at least one weight related condition, and in adolescents aged 12 and older
- Reducing the risk of major cardiovascular events (heart attack, stroke, cardiovascular death) in adults with established heart disease and obesity or overweight
- Noncirrhotic MASH (metabolic dysfunction associated steatohepatitis) with liver fibrosis, under accelerated approval
Mounjaro (tirzepatide, Eli Lilly) is FDA approved for:
- Type 2 diabetes in adults and pediatric patients aged 10 and older, as an adjunct to diet and exercise
- That is the complete list. Weight loss is not an approved indication for Mounjaro in the US
Zepbound (tirzepatide, Eli Lilly) is FDA approved for:
- Chronic weight management in adults with obesity or overweight with at least one weight related condition
- Moderate to severe obstructive sleep apnea in adults with obesity
In the United Kingdom
Mounjaro (tirzepatide) is MHRA licensed for both:
- Type 2 diabetes (approved October 2022)
- Weight loss and weight management in adults aged 18 and over (approved November 2023, NICE recommended December 2024)
This is the core of the confusion. In the UK, this is a legitimate weight loss comparison. In the US, it is not. The US equivalent would be Wegovy versus Zepbound, and that comparison has its own dedicated article here.
| Factor | Wegovy (semaglutide) | Mounjaro (tirzepatide) |
|---|---|---|
| Manufacturer | Novo Nordisk | Eli Lilly |
| Drug class | GLP-1 receptor agonist | Dual GIP and GLP-1 receptor agonist |
| US FDA approved for weight loss | Yes | No (Zepbound carries this approval) |
| UK MHRA approved for weight loss | Yes | Yes (November 2023) |
| US FDA approved for diabetes | As Ozempic (separate brand) | Yes |
| Cardiovascular risk reduction | Yes (FDA approved, SELECT trial) | Not yet approved under any brand |
| MASH indication | Yes (accelerated approval) | No |
| Available forms | Injection and oral tablet (US) | Injection only |
The Molecules: Same Class, Different Mechanism
Both are incretin based therapies, but the receptor activity is different.
Semaglutide (Wegovy) is a GLP-1 receptor agonist. It activates one gut hormone pathway, glucagon like peptide 1, which slows gastric emptying, reduces appetite, and stimulates insulin when blood sugar is elevated.
Tirzepatide (Mounjaro/Zepbound) is a dual GIP and GLP-1 receptor agonist. It activates both the GLP-1 pathway and the GIP (glucose dependent insulinotropic polypeptide) pathway. This dual mechanism is the likely explanation for why tirzepatide produces larger weight reductions in clinical trials.
Head to Head: What the Trials Show
SURMOUNT-5, published in the New England Journal of Medicine in 2025, is the only head to head trial comparing these two molecules for weight loss. Over 72 weeks in adults with obesity but without diabetes:
- Tirzepatide produced a mean weight reduction of 20.2%
- Semaglutide produced a mean weight reduction of 13.7%
- Tirzepatide met its primary endpoint and all five key secondary endpoints, including waist circumference
The weight loss advantage was consistent across subgroups. Notably, weight loss in women was greater than in men for both drugs, a reversal of patterns seen in earlier tirzepatide only trials.
What Wegovy has that tirzepatide does not:
The SELECT trial, published in the New England Journal of Medicine in 2023, demonstrated that semaglutide reduced the risk of major cardiovascular events by 20% in adults with obesity or overweight and established cardiovascular disease, but without diabetes. This led to Wegovy's FDA approved cardiovascular indication. No tirzepatide product has this approval yet, though cardiovascular outcome trials are ongoing.
No waiting list. No insurance needed.
Frequently Asked Questions
Is Mounjaro approved for weight loss in the US?
No. In the United States, Mounjaro is FDA approved only for Type 2 diabetes. The same molecule, tirzepatide, is sold as Zepbound for weight management. In the UK, Mounjaro is approved for both diabetes and weight loss.
Which drug produces more weight loss, Wegovy or Mounjaro?
In the SURMOUNT-5 trial, tirzepatide (the molecule in Mounjaro and Zepbound) produced roughly 20% body weight loss compared with roughly 14% for semaglutide (the molecule in Wegovy) over 72 weeks.
Why do UK websites say Mounjaro is for weight loss when US sources say it is not?
Because the UK MHRA approved Mounjaro for weight management in November 2023. The US FDA did not. In the US, the same molecule is sold under a separate brand name, Zepbound, for weight management.
Does Wegovy protect your heart?
Yes. The SELECT trial demonstrated that semaglutide (Wegovy) reduced major cardiovascular events by 20% in adults with established heart disease and obesity or overweight. Tirzepatide does not yet have this approval under any brand name.
Can I take Wegovy as a pill instead of an injection?
Yes. Wegovy is now available as both a once weekly injection and a once daily oral tablet in the US. Tirzepatide (Mounjaro and Zepbound) remains injection only.
If I am in the US and want tirzepatide for weight loss, what should I ask for?
Ask your physician about Zepbound, which is the tirzepatide brand approved for weight management in the US. Mounjaro contains the same molecule but is approved only for Type 2 diabetes.
Dosing: How Each Drug Scales
Both are once weekly injections, but the titration schedules and maintenance ranges differ.
| Dosing Detail | Wegovy (semaglutide) | Mounjaro (tirzepatide) |
|---|---|---|
| Starting dose | 0.25 mg weekly (injection); 1.5 mg daily (tablet) | 2.5 mg weekly |
| Escalation schedule | Every 4 weeks through 5 steps (injection); every 30 days through 4 steps (tablet) | Every 4 weeks in 2.5 mg increments |
| Maintenance dose | 2.4 mg weekly (injection); 25 mg daily (tablet) | 5 mg to 15 mg weekly (physician selected) |
| Time to maintenance | 16 weeks (injection); 12 weeks (tablet) | Minimum 8 weeks, up to 20 weeks depending on target dose |
| Available forms | Prefilled pen, oral tablet | Prefilled pen, KwikPen, vial |
Mounjaro's wider dose range (up to 15 mg) gives physicians more room to titrate for individual response. Wegovy's oral tablet option is a meaningful differentiator for patients who prefer not to inject.
Use Cases: Which Drug Fits Which Situation
You want maximum weight loss and are in the US. The head to head comparison you want is Wegovy vs Zepbound, not Wegovy vs Mounjaro. Both are on label for weight management. Mounjaro is not. See our Ozempic vs Zepbound comparison for that analysis.
You are in the UK and choosing between two approved weight loss drugs. This is the one scenario where this comparison is exactly what it looks like. Tirzepatide (Mounjaro) produced greater weight loss in SURMOUNT-5. Semaglutide (Wegovy) has the cardiovascular protection data from SELECT. Your clinician weighs both against your specific history.
You have Type 2 diabetes and want tirzepatide. Mounjaro is the correct on label choice in the US. It is the same molecule approved for your diagnosis, and far more likely to be covered by insurance than Zepbound.
You have Type 2 diabetes and want semaglutide. Ozempic is the diabetes brand. Wegovy is the weight management brand. Same molecule, different approved uses, different coverage pathways.
You want to avoid injections entirely. Wegovy is the only option here with an oral tablet form. Tirzepatide is injection only under both brand names.
You have established heart disease and want cardiovascular protection. Wegovy has the FDA approved indication from the SELECT trial, covering patients with and without diabetes. Tirzepatide does not yet have this under any brand.
Side Effects
Both cause gastrointestinal side effects through the same mechanism of slowed gastric emptying. Tirzepatide's rates are measurably higher.
| Side Effect | Wegovy (semaglutide 2.4 mg) | Mounjaro/Zepbound (tirzepatide) |
|---|---|---|
| Nausea | 44% (during titration, lower at maintenance) | 25 to 29% |
| Diarrhea | 30% | 19 to 23% |
| Vomiting | 24% | 8 to 13% |
| Constipation | 24% | 11 to 17% |
| Stomach pain | 20% | 9 to 10% |
A note on these numbers: Wegovy's rates above reflect the full titration period through the STEP trials, which captured the worst of the dose escalation phase. At maintenance doses, rates are lower. The comparison is not perfectly apples to apples, but the general pattern of overlapping GI events is consistent across both molecules.
Both carry the same serious warnings: boxed warning about thyroid C cell tumors, risks of pancreatitis, gallbladder problems, kidney injury from dehydration, and allergic reactions. Neither should be used by anyone with a personal or family history of medullary thyroid carcinoma or Multiple Endocrine Neoplasia syndrome type 2.
Related Comparisons
- Ozempic vs Zepbound: Why You Are Comparing Two Drugs Approved for Different Things
- Wegovy vs Trulicity: An Older GLP-1 Against a Newer One
- Zepbound vs Trulicity: Two Very Different Generations of GLP-1
Medication guides: Wegovy, Mounjaro, Zepbound, Ozempic
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