The most common question in the GLP-1 world is some variation of: "What's the difference between Ozempic, Wegovy, and Mounjaro?" The confusion is understandable — these names get thrown around interchangeably, and the actual distinctions matter more than most articles bother to explain.

Let's break it down clearly.

The Quick Answer

Ozempic and Wegovy are the same drug (semaglutide) at different doses, approved for different conditions. Mounjaro is a different drug (tirzepatide) that works through a related but distinct mechanism. All three cause significant weight loss. The details matter if you're trying to decide which to ask your doctor about.

Semaglutide: The Molecule Behind Ozempic and Wegovy

Both Ozempic and Wegovy contain semaglutide, a GLP-1 receptor agonist made by Novo Nordisk. The difference is straightforward:

  • Ozempic is FDA-approved for Type 2 diabetes. Maximum dose: 2.0mg per week.
  • Wegovy is FDA-approved for chronic weight management. Maximum dose: 2.4mg per week.

Same company. Same molecule. Same injection pen design. Wegovy simply goes to a higher dose and carries the weight loss indication on its label, which means insurance is more likely to cover it specifically for weight management (though coverage varies wildly — more on that below).

When people say they're "using Ozempic for weight loss," what's usually happening is off-label prescribing — a doctor prescribes the diabetes version for weight management because Wegovy has been harder to get due to supply shortages. This is legal and common, but it means the maximum dose tops out at 2.0mg rather than 2.4mg.

How Semaglutide Works

Semaglutide mimics the GLP-1 hormone your gut naturally produces after eating. It suppresses appetite at the brain level, slows gastric emptying, and improves insulin signaling. For a deeper dive, see our full explanation of how GLP-1 medications work.

Tirzepatide: The Molecule Behind Mounjaro (and Zepbound)

Mounjaro contains tirzepatide, made by Eli Lilly. It's not just "another GLP-1 drug" — it works through a dual mechanism:

  • GLP-1 receptor agonist (same pathway as semaglutide)
  • GIP receptor agonist (glucose-dependent insulinotropic polypeptide — a second gut hormone)

By activating both the GLP-1 and GIP receptors, tirzepatide appears to produce greater appetite suppression and metabolic improvement than GLP-1 alone. Think of it as hitting two switches instead of one.

Like the Ozempic/Wegovy split, Eli Lilly has two brand names:

  • Mounjaro — FDA-approved for Type 2 diabetes
  • Zepbound — FDA-approved for chronic weight management

Same molecule, different label. Zepbound is the weight-loss branded version of tirzepatide.

Head-to-Head: Weight Loss Results From Clinical Trials

This is what most people really want to know. Here's the data from the landmark trials:

Semaglutide (STEP 1 Trial)

  • Participants: 1,961 adults with BMI ≥30 (or ≥27 with comorbidity), without diabetes
  • Duration: 68 weeks
  • Average weight loss: 14.9% of body weight (vs 2.4% placebo)
  • Percentage losing ≥10%: 69.1% of participants
  • Percentage losing ≥20%: 32.0% of participants

Tirzepatide (SURMOUNT-1 Trial)

  • Participants: 2,539 adults with BMI ≥30 (or ≥27 with comorbidity), without diabetes
  • Duration: 72 weeks
  • Average weight loss at highest dose (15mg): 22.5% of body weight (vs 2.4% placebo)
  • Percentage losing ≥10% (15mg dose): 89% of participants
  • Percentage losing ≥20% (15mg dose): 57% of participants

The numbers favor tirzepatide, and the difference is not small. At the highest dose, SURMOUNT-1 participants lost roughly 50% more weight than STEP 1 participants. However, there are important caveats:

  • These are different trials with different patient populations. A true head-to-head comparison requires a trial designed specifically to compare them (these are ongoing).
  • Individual responses vary enormously. Some people respond better to semaglutide, others to tirzepatide.
  • The side effect profiles are similar but not identical.

Side Effects Compared

The side effect profiles are broadly similar — both are GI-dominant:

  • Nausea: ~44% semaglutide vs ~31% tirzepatide (tirzepatide may be slightly better tolerated at equivalent efficacy levels)
  • Diarrhea: ~30% for both
  • Constipation: ~24% semaglutide vs ~23% tirzepatide
  • Vomiting: ~24% semaglutide vs ~12% tirzepatide

Most side effects for both drugs are transient — worst during dose escalation, improving as your body adjusts. See our guide on what to expect your first month for practical management strategies.

Cost: The Elephant in the Room

Without insurance, all of these medications are expensive:

  • Ozempic: ~$900-1,000/month
  • Wegovy: ~$1,300-1,400/month
  • Mounjaro: ~$1,000-1,100/month
  • Zepbound: ~$1,000-1,100/month

Insurance coverage is highly variable. Some plans cover Wegovy and/or Zepbound for weight management if you meet BMI criteria. Many plans cover Ozempic and Mounjaro for diabetes but not for weight loss. Employer plans, Medicare Part D, and state Medicaid programs all differ.

Telehealth providers like Hims, Ro, and Found have emerged as popular options, often offering compounded versions or manufacturer savings programs that bring costs down significantly. These typically run $200-500/month depending on the provider and medication.

For a detailed look at costs and savings strategies, see our guide to GLP-1 medication costs.

FDA Approval Status (2025)

BrandMoleculeApproved ForMaker
OzempicSemaglutideType 2 DiabetesNovo Nordisk
WegovySemaglutideWeight ManagementNovo Nordisk
MounjaroTirzepatideType 2 DiabetesEli Lilly
ZepboundTirzepatideWeight ManagementEli Lilly

Wegovy also carries an FDA-approved indication for cardiovascular risk reduction, based on the SELECT trial showing a 20% reduction in major cardiac events. No other GLP-1 currently has this indication.

Which Should You Ask Your Doctor About?

There's no universal "best" choice. Here's a simplified decision framework:

  • If your primary goal is weight loss and you want the strongest data: Tirzepatide (Zepbound/Mounjaro) has produced the largest weight loss in trials so far.
  • If you have cardiovascular risk factors: Semaglutide (Wegovy) has the SELECT trial data supporting cardiac benefit.
  • If cost is the primary concern: Ask about manufacturer savings programs, compounded options, and which drug your insurance actually covers. The "best" drug is the one you can access and afford consistently.
  • If you've tried one and had intolerable side effects: Switching to the other class (GLP-1 only vs dual agonist) is a reasonable strategy, as the mechanisms differ enough that tolerability may differ too.

The most important thing is having this conversation with a licensed provider who can evaluate your specific health profile. Tools like MeOnGLP can help you visualize the potential outcome, but the medication decision should always involve a medical professional.