2026-05-27 · glp-1, medications, comparison, semaglutide, tirzepatide

GLP-1 Weight Loss Medications Compared: Ozempic vs Wegovy vs Mounjaro vs Zepbound

Quick answer: Tirzepatide-based drugs (Mounjaro and Zepbound) produce the largest average weight loss in published trials — roughly 20% of body weight at the highest dose — while semaglutide-based drugs (Ozempic and Wegovy) are the longer-established option with about 15% average loss. The choice usually comes down to brand vs indication: Wegovy and Zepbound are FDA-approved for obesity, Ozempic and Mounjaro for diabetes. Insurance coverage, prior authorization rules, and dose ceiling drive most real-world decisions.

If you are trying to compare GLP-1 weight loss medications, you are looking at two active ingredients — semaglutide and tirzepatide — sold under four brand names. This guide breaks down what is the same, what is different, and how clinicians actually choose between them. For background on the drug class, start with the GLP-1 weight loss overview.

Side-by-side comparison

Trial averages are not promises. STEP 1 enrolled adults with obesity without diabetes; SURMOUNT-1 enrolled a similar population for tirzepatide. People with type 2 diabetes typically lose less weight on the same drug. Individual results depend on dose, adherence, lifestyle support, and biology.

Drug-by-drug summaries

Ozempic (semaglutide)

Ozempic is semaglutide marketed for type 2 diabetes. It is approved at doses up to 2.0 mg weekly, which is lower than the 2.4 mg used for Wegovy. In the SUSTAIN trials, Ozempic improved blood sugar control and produced modest weight loss — about 4 to 6 kg on average in diabetes populations.

Ozempic is widely prescribed off-label for weight loss in people without diabetes, but insurance typically only covers it for its diabetes indication. People prescribed Ozempic for weight loss often pay out of pocket, and the dose ceiling means they cap out below what Wegovy can reach.

The active ingredient is identical to Wegovy. The differences are dose, FDA labeling, and insurance pathway. For a focused look at how Ozempic and Wegovy compare, see Ozempic vs Wegovy, and for side effects see Ozempic side effects.

Wegovy (semaglutide)

Wegovy is the obesity-indication brand of semaglutide. It is FDA-approved for chronic weight management in adults with a BMI of 30 or higher, or 27 or higher with a weight-related condition. It is also approved for adolescents aged 12 and older with obesity, and for cardiovascular risk reduction in adults with cardiovascular disease and obesity or overweight.

In the STEP 1 trial published in the New England Journal of Medicine, adults on Wegovy 2.4 mg weekly lost about 15% of body weight at 68 weeks, compared with about 2.4% on placebo. STEP 4 showed that continued treatment was needed to maintain that loss — when people switched to placebo, they regained a substantial share.

Wegovy uses a slow titration schedule that takes roughly 4 to 5 months to reach the 2.4 mg maintenance dose. Most insurance plans require prior authorization, documented BMI, and prior lifestyle attempts. For the underlying active ingredient, see semaglutide for weight loss.

Mounjaro (tirzepatide)

Mounjaro is tirzepatide marketed for type 2 diabetes. Tirzepatide is unusual in this class because it activates both the GLP-1 and the GIP receptors — a dual agonist instead of a single agonist. In the SURPASS-2 trial, Mounjaro produced greater A1c reduction and greater weight loss than semaglutide 1 mg in people with type 2 diabetes.

Like Ozempic, Mounjaro is sometimes prescribed off-label for weight loss when Zepbound is not covered or available, but insurance coverage outside the diabetes indication is rare. The titration schedule and dose levels are the same as Zepbound (2.5 mg starting dose, maintenance options at 5, 10, or 15 mg weekly), and the molecule is identical.

People with type 2 diabetes who are also targeting weight loss sometimes prefer Mounjaro because a single prescription can address both goals and may have better coverage.

Zepbound (tirzepatide)

Zepbound is the obesity-indication brand of tirzepatide. It was approved by the FDA in late 2023 for chronic weight management in adults meeting standard BMI criteria, and later for moderate-to-severe obstructive sleep apnea in adults with obesity.

In SURMOUNT-1, adults without diabetes on Zepbound 15 mg weekly lost about 20% of body weight at 72 weeks, compared with about 3% on placebo. The 5 mg and 10 mg doses produced about 15% and 19% loss respectively. SURMOUNT-2 showed smaller but still substantial loss in people with type 2 diabetes. In 2025, SURMOUNT-5 reported a direct head-to-head comparison favoring tirzepatide over semaglutide for weight loss in adults with obesity without diabetes.

Zepbound is the newest of the four brands, so long-term real-world data is still accumulating. Eli Lilly has also offered a direct-to-consumer vial program for some Zepbound doses, which can lower the out-of-pocket cost compared with the auto-injector pen.

Semaglutide vs tirzepatide: the active-ingredient story

The four brand names cover two distinct molecules.

Semaglutide is a GLP-1 receptor agonist. It mimics the hormone GLP-1, slowing stomach emptying, signaling fullness, and reducing food intake. It has been on the U.S. market since 2017 for diabetes and 2021 for obesity, so it has the longest post-approval safety record in this class.

Tirzepatide is a dual GIP/GLP-1 receptor agonist. It activates the GLP-1 receptor like semaglutide and adds activation of the GIP receptor, which is thought to contribute to additional appetite suppression and metabolic effects. The dual mechanism is the leading explanation for the larger average weight loss seen in tirzepatide’s phase 3 program.

For a deeper head-to-head on the active ingredients, see semaglutide vs tirzepatide.

How to choose

There is no single “best” GLP-1. Most patients land on a drug for reasons that have little to do with the underlying molecule.

• Insurance and cost. Coverage drives most decisions. Many commercial plans cover one obesity-indication drug (Wegovy or Zepbound) but not the other. Medicare Part D does not currently cover GLP-1s for obesity alone, though it covers them for diabetes and for cardiovascular risk reduction in eligible patients. Confirm formulary placement, prior authorization criteria, and step therapy requirements before settling on a drug.
• GI side effect tolerance. All GLP-1s share a similar GI profile — nausea, constipation, diarrhea, vomiting, especially during dose escalation. Slow titration and small, lower-fat meals help. If one drug produces intolerable nausea, clinicians sometimes switch to the other class member.
• Injection device preference. Wegovy and Ozempic use Novo Nordisk pen devices. Zepbound and Mounjaro use Eli Lilly pen devices, and Zepbound is also available in single-dose vials in some U.S. programs. Pen design matters more to some patients than others.
• Off-label realities. Ozempic and Mounjaro are FDA-approved for diabetes, so insurance coverage for weight loss alone is rare. Some clinicians still prescribe them off-label, but expect to pay out of pocket and to cap below the maintenance doses studied for obesity.
• When each is typically prescribed. A patient with type 2 diabetes plus obesity may end up on Ozempic or Mounjaro. A patient without diabetes meeting BMI criteria is more likely to be prescribed Wegovy or Zepbound. A patient with cardiovascular disease and obesity may be steered toward Wegovy for its FDA-approved cardiovascular indication.

For the broader landscape of approved options, see the prescription weight loss medications overview. If you are weighing medication against an operation, see bariatric surgery vs GLP-1 medications for an evidence-based side-by-side on expected loss, durability, and cost.

Safety and contraindications

All GLP-1 receptor agonists share a similar safety profile. The most important shared warnings:

• Boxed warning for thyroid C-cell tumors. All four drugs carry a boxed warning based on rodent studies. They are contraindicated in people with a personal or family history of medullary thyroid carcinoma (MTC) or multiple endocrine neoplasia syndrome type 2 (MEN2).
• Pancreatitis history. A prior episode of pancreatitis is a relative contraindication; discuss with your prescriber.
• Pregnancy and breastfeeding. These drugs are not recommended in pregnancy, while breastfeeding, or for people planning pregnancy in the near term. A washout period is recommended before conception.
• Gallbladder disease. Rapid weight loss raises the risk of gallstones; people with prior gallbladder disease should discuss risk with their clinician.
• Hypoglycemia risk. Mainly in people who also take insulin or sulfonylureas — dose adjustments may be needed for the other medications.
• GI side effects. Nausea, vomiting, constipation, and diarrhea are common, especially during titration. Dehydration from vomiting or diarrhea has been linked to acute kidney injury in some cases.

For a broader view of class safety, see weight loss drug safety, and for a deeper drug-specific look at side effects, see Ozempic side effects.

Frequently asked questions

Which GLP-1 causes the most weight loss? On published averages, tirzepatide (Zepbound at 15 mg) produced the largest loss — about 20–22% of body weight at 72 weeks in SURMOUNT-1 — followed by Wegovy at about 15% in STEP 1. Individual results vary, and the highest dose is not always the right dose for a given person.

What’s the difference between Ozempic, Wegovy, Mounjaro, and Zepbound? Ozempic and Wegovy are both semaglutide; Mounjaro and Zepbound are both tirzepatide. Within each pair, the difference is FDA-approved use (diabetes vs obesity), dose ceiling, and insurance pathway. The molecules within each pair are identical.

Is tirzepatide stronger than semaglutide? At the doses studied, yes on average. SURPASS-2 in diabetes and SURMOUNT-5 in obesity both showed greater weight reduction with tirzepatide. The dual GIP/GLP-1 mechanism is the leading explanation. Individual results still vary widely.

Which is cheapest without insurance? U.S. list prices for all four sit in the low four figures per month. Manufacturer direct-pay vial programs (such as the Eli Lilly Zepbound vial program) have made some doses cheaper than auto-injector pens. Cost without insurance is broadly similar across all four; the real difference comes from coverage.

Can I switch from one GLP-1 to another? Yes, under clinician guidance. Reasons include insurance changes, intolerable side effects, supply shortages, or a plateau. Never combine two GLP-1 medications, and do not switch on your own — your prescriber will choose a safe starting dose on the new drug.

Can I take a GLP-1 if I don’t have diabetes? Yes. Wegovy and Zepbound are FDA-approved specifically for chronic weight management in adults meeting BMI criteria. Ozempic and Mounjaro are diabetes drugs and are sometimes used off-label, though insurance rarely covers that use.

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