Zepbound vs Wegovy: Complete Comparison

SURMOUNT-5 is the trial everyone was waiting for — a direct head-to-head comparison of tirzepatide (Zepbound) vs semaglutide (Wegovy) in adults with obesity.

Results over 72 weeks:

• Zepbound (tirzepatide 15mg): 20.2% body weight loss
• Wegovy (semaglutide 2.4mg): 13.7% body weight loss

That's a 47% relative advantage for Zepbound — an additional 6.5 percentage points of body weight, translating to roughly 15 additional pounds lost on average.

Proportion reaching milestones:

• ≥5% weight loss: 94% (Zepbound) vs 85% (Wegovy)
• ≥10% weight loss: 82% (Zepbound) vs 66% (Wegovy)
• ≥15% weight loss: 66% (Zepbound) vs 42% (Wegovy)
• ≥20% weight loss: 47% (Zepbound) vs 22% (Wegovy)

On pure weight loss, Zepbound is the clear winner. Nearly half of Zepbound patients lost 20% or more of their body weight, compared to only 1 in 5 on Wegovy.

The efficacy difference comes from pharmacology:

• Wegovy (semaglutide): Activates the GLP-1 receptor only. This reduces appetite, slows gastric emptying, and improves insulin sensitivity.
• Zepbound (tirzepatide): Activates both the GLP-1 and GIP receptors. The dual mechanism enhances energy expenditure, improves fat metabolism, and provides stronger appetite suppression than GLP-1 alone.

GIP's role: Glucose-dependent insulinotropic polypeptide (GIP) is a gut hormone that, when combined with GLP-1 agonism, appears to amplify weight loss through pathways that semaglutide alone doesn't fully engage — including improved lipid handling, greater thermogenesis, and potentially better lean mass preservation.

Practical takeaway: Zepbound's dual mechanism isn't marketing spin — it's a genuine pharmacological advantage confirmed by head-to-head trial data. However, not every patient responds equally. Some patients do very well on semaglutide alone.

This is where Wegovy has a decisive advantage.

The SELECT trial (published 2023, NEJM) demonstrated that semaglutide 2.4mg injection reduced major adverse cardiovascular events (MACE — heart attack, stroke, CV death) by 20% in patients with established cardiovascular disease and overweight/obesity, independent of weight loss.

This was groundbreaking: it proved that Wegovy isn't just a weight loss drug — it's a cardiovascular risk reduction drug.

Zepbound has no completed CV outcomes trial. Lilly's SURPASS-CVOT trial is evaluating tirzepatide for cardiovascular outcomes, but results aren't expected until 2027. Until then, we cannot make cardiovascular claims for Zepbound.

What this means in practice:

• For patients with established heart disease, prior stroke, or high CV risk: Wegovy has evidence-based cardioprotection. Zepbound doesn't — yet.
• For patients whose primary goal is weight loss without specific CV concerns: Zepbound's superior efficacy may be more relevant.
• Many cardiologists now specifically prescribe Wegovy for its CV benefit, regardless of weight loss goals.

Both are expensive at list price, but real-world costs vary significantly:

• Zepbound: $1,086/mo list price. LillyDirect self-pay: $499/mo (flat, all doses). Savings card: $25/mo for eligible commercially insured patients.
• Wegovy injection: ~$1,349/mo list price. Savings card: $25/mo for eligible patients.
• Wegovy pill: $149–299/mo self-pay — much cheaper than the injection.

For uninsured self-pay patients: Zepbound at $499/mo (LillyDirect) is more affordable than Wegovy injection ($1,349/mo). But if you're willing to use the Wegovy pill instead of injection, costs drop to $149–299/mo.

Insurance coverage: Varies widely by plan. Some insurers cover one but not the other. Prior authorization is common for both. Check your specific plan.

Both cause GI side effects typical of GLP-1 medications, but head-to-head data suggests Zepbound is somewhat better tolerated:

From SURMOUNT-5 (head-to-head):

• Nausea: Zepbound ~24% vs Wegovy ~28%
• Diarrhea: Zepbound ~21% vs Wegovy ~17%
• Vomiting: Zepbound ~13% vs Wegovy ~15%
• Discontinuation due to AEs: Zepbound ~3.5% vs Wegovy ~5.0%

From individual trials:

• Zepbound (SURMOUNT-1): Nausea ~28%, diarrhea ~23%, constipation ~11%
• Wegovy (STEP-1): Nausea ~44%, diarrhea ~30%, vomiting ~24%

Zepbound appears modestly better tolerated. The discontinuation rate due to side effects was lower in SURMOUNT-5. The GIP component of tirzepatide may buffer some of the GI effects that pure GLP-1 agonism causes.

Choose Zepbound if:

• Maximum weight loss is your primary goal
• You don't have established cardiovascular disease
• You tolerated GLP-1 medications before but want more efficacy
• You're paying self-pay and LillyDirect's $499/mo works for your budget
• Lean mass preservation is important to you

Choose Wegovy if:

• You have established cardiovascular disease or high CV risk (SELECT trial evidence)
• Your cardiologist recommends semaglutide specifically
• You prefer the option to switch to a pill form later (Wegovy pill)
• Your insurance covers Wegovy but not Zepbound
• You've responded well to semaglutide in the past (Ozempic, Rybelsus)

The nuanced answer: For most patients without cardiovascular disease, Zepbound's superior efficacy makes it the stronger choice. For patients with cardiovascular disease, Wegovy's proven cardioprotection may outweigh Zepbound's weight loss advantage. Discuss with your physician.