Ozempic vs Wegovy vs Zepbound: Which GLP-1 Is Right for You?

This draft is pending qualified medical review before publication.

Ozempic, Wegovy, Mounjaro, and Zepbound are brand names built on two molecules. Ozempic and Wegovy both contain semaglutide, a GLP-1 (glucagon-like peptide-1) receptor agonist. Mounjaro and Zepbound both contain tirzepatide, a dual GLP-1/GIP receptor agonist. All four are once-weekly subcutaneous injections. The brand name someone is prescribed usually depends less on the molecule and more on which FDA indication applies to them: type 2 diabetes (Ozempic, Mounjaro) or chronic weight management (Wegovy, Zepbound). That indication, not the drug's chemistry, is what determines whether insurance is likely to cover it.

The short answer

Semaglutide (Wegovy) and tirzepatide (Zepbound) are both FDA-approved for chronic weight management in adults with obesity, or overweight plus a weight-related condition, as of 2025. In separate Phase 3 trials, not a head-to-head comparison, tirzepatide has produced numerically greater average weight loss than semaglutide at the highest approved doses. Semaglutide currently has a dedicated cardiovascular outcomes trial in people with obesity and established heart disease showing a reduction in major cardiovascular events; tirzepatide's comparable outcomes trial had not been published as of this writing. Neither difference has been tested in a single randomized trial that put the two drugs head to head, so cross-trial comparisons should be read as suggestive, not definitive.

Disambiguating the four brand names

Prescribing Ozempic or Mounjaro for weight loss in someone without type 2 diabetes is off-label. It is done, but it falls outside the FDA-reviewed indication for that specific product, and most insurers will not pay for an off-label prescription. This is a labeling and coverage distinction, not evidence that the drug behaves differently at an equivalent dose.

How much weight loss should someone actually expect?

Weight-loss percentages from obesity trials are widely quoted, and it is worth being precise about what they mean and where the uncertainty lives.

Semaglutide's pivotal obesity trial (STEP-1) followed adults without diabetes for 68 weeks and reported average weight loss in the mid-teens as a percentage of body weight on the 2.4 mg dose, compared with a low single-digit percentage on placebo. Tirzepatide's pivotal obesity trial (SURMOUNT-1) followed adults for 72 weeks and reported average weight loss around one-fifth of body weight at the highest 15 mg dose. These are the numbers most often cited to say tirzepatide "works better," and the direction is probably real, but the exact figures should be confirmed against the original trial publications before being restated as precise numbers in a clinical or patient-facing context, since this draft treats all specific percentages inherited from prior sourcing as unverified pending primary-literature check.

What is more defensible without a specific percentage: both drugs produce substantially more average weight loss than older pharmacotherapy such as phentermine or phentermine-topiramate, both require ongoing use to sustain results, and neither trial population is identical to any individual patient, so an individual's response can fall well outside the group average in either direction.

Cardiovascular and diabetes evidence: not identical between the two drugs

Semaglutide has a completed, published cardiovascular outcomes trial (the SELECT trial) in adults with overweight or obesity and established cardiovascular disease, without diabetes, showing a reduction in major adverse cardiovascular events versus placebo. This is trial-level evidence specific to semaglutide 2.4 mg, and it is one of the few outcomes trials in obesity pharmacotherapy that looks at hard cardiovascular events rather than weight or A1C alone.

Tirzepatide does not yet have a published cardiovascular outcomes trial of comparable scale in this population. That is a gap in the evidence base, not evidence that tirzepatide lacks cardiovascular benefit; it simply has not been tested and reported the same way yet. For a patient with established cardiovascular disease, this asymmetry in the evidence is a legitimate reason a clinician might lean toward semaglutide until tirzepatide's outcomes data are available, and that reasoning should be revisited once those results are published.

For glycemic control, both drugs lower A1C meaningfully in people with type 2 diabetes, with tirzepatide's dual incretin mechanism generally reported to produce somewhat larger average A1C reductions in diabetes trials. The size of that gap and its clinical significance for an individual patient depend on baseline A1C, other diabetes medications, and renal function, and should be worked out with the prescribing clinician rather than inferred from a trial average.

A decision-relevant comparison

The table below is organized around the variables that actually change a prescribing decision, not around brand marketing points.

Mounjaro vs Zepbound and Ozempic vs Wegovy: the same pattern twice

Mounjaro and Zepbound are the identical tirzepatide molecule at the identical dose range. The only difference is the FDA indication on the label: diabetes for Mounjaro, weight management for Zepbound. The same is true of Ozempic and Wegovy with semaglutide. In both pairs, a patient with type 2 diabetes and obesity may reasonably be prescribed the diabetes-labeled brand and see weight loss as a secondary benefit, while a patient with obesity and no diabetes generally needs the weight-management brand for any realistic chance at insurance coverage. This is an access and labeling distinction, not a difference in what the drug does in the body.

GLP-1 drugs versus phentermine

Phentermine is an older sympathomimetic stimulant approved for short-term use (traditionally up to about 12 weeks) because of cardiovascular stimulant effects like elevated heart rate and blood pressure. In short trials, its average weight loss is well below what GLP-1 or dual-agonist drugs produce over a comparable or longer period. Phentermine-topiramate extended-release narrows that gap somewhat over a longer treatment window but still trails tirzepatide's reported ceiling.

Phentermine remains a reasonable option in specific circumstances: when a patient has a contraindication to GLP-1 or dual-agonist therapy, such as a personal or family history of medullary thyroid carcinoma or MEN2 syndrome, when cost is the deciding constraint (generic phentermine can run under $30 a month versus roughly ten times that or more for branded semaglutide or tirzepatide), or as a short-term bridge before starting an injectable. The tradeoff is real: substantially less average weight loss, and none of the cardiovascular outcomes evidence that exists for semaglutide.

Side effects and who should not start either drug

Gastrointestinal side effects, nausea, vomiting, diarrhea, and constipation, are the dominant tolerability issue for both semaglutide and tirzepatide. They are most common during dose escalation and typically ease within the first several weeks at a stable dose, though not for everyone.

Both drug classes carry FDA boxed warnings related to thyroid C-cell tumors seen in rodent studies; whether this translates to human risk at clinical doses has not been established, and both are contraindicated in anyone with a personal or family history of medullary thyroid carcinoma or MEN2 syndrome. Pancreatitis is an uncommon but recognized risk with both drugs, and a prior history of pancreatitis warrants caution. Rapid weight loss from any cause increases gallstone risk, and the FDA has also added labeling language about reports of delayed gastric emptying (gastroparesis-like symptoms) with GLP-1 receptor agonists, which matters for anyone with pre-existing gastric motility problems.

Pregnancy is an absolute contraindication for both drugs; patients should discuss timing with their prescriber well before attempting conception. Patients on insulin or sulfonylureas need those doses reassessed when starting a GLP-1 or dual-agonist drug, because the combination raises hypoglycemia risk. People with advanced kidney disease have limited safety data and should have this conversation directly with a nephrologist or their prescribing clinician, not infer safety from population averages.

None of this is dosing advice. Titration schedules, dose adjustments, and decisions about starting, pausing, or restarting therapy should be made with a prescribing clinician who knows the patient's full history.

What happens after stopping

A consistent finding across obesity pharmacotherapy trials, for both semaglutide and tirzepatide, is that stopping the drug leads to substantial weight regain within about a year, though the exact proportion regained varies by study and should not be treated as a fixed number without checking the specific trial. This is consistent with the broader clinical view of obesity as a chronic condition in which appetite-regulating hormones do not simply reset to a pre-treatment baseline after weight loss. The practical implication is that these medications are generally intended as long-term therapy rather than a finite course, and a patient considering stopping should have a maintenance plan, whether that means continuing medication at a lower dose, adding structured lifestyle support, or both, discussed with their clinician beforehand.

A separate and growing line of evidence looks at how these drugs perform when layered onto structured lifestyle intervention rather than compared against it. A narrative synthesis of second-generation obesity medications in the context of lifestyle treatment argues that diet, activity, and behavioral support remain part of the standard of care alongside pharmacotherapy rather than being replaced by it, and that stacking the two is where much of the durable benefit is expected to come from (Chao and colleagues, 2026). This is an expert narrative review and reasoning-based synthesis, not a new randomized trial, and its conclusions should be read as guideline-adjacent judgment rather than trial-level proof.

Emerging, unproven uses worth naming honestly

Obesity is closely linked to conditions like obstructive sleep apnea and weight-bearing joint pain, and there is active interest in whether GLP-1 or dual-agonist therapy improves these conditions beyond what weight loss alone would predict. A 2026 narrative review examined incretin-based therapies in obesity-related obstructive sleep apnea and described the evidence as still developing, spanning mechanistic plausibility more than confirmed clinical outcomes across diverse study designs (narrative review, 2026). A companion narrative review and expert opinion piece considered GLP-1-based therapy for obesity-related low back and knee pain and again characterized the evidence as preliminary and mechanistic rather than established (narrative review and expert opinion, 2026). Neither of these is an FDA-approved indication, and patients should not expect a GLP-1 prescription to specifically treat sleep apnea or joint pain outside of the general effect of weight loss itself, which is separately established.

Access and compounding, as of this writing

Compounded versions of semaglutide and tirzepatide became common during the FDA drug shortage period covering 2022 through 2024. Once the FDA removes a drug from its shortage list, compounding pharmacies operating under standard 503A/503B rules are no longer permitted to produce copies of that exact molecule for general use. Shortage status changes over time, so a patient or clinician relying on this for a coverage or safety decision should check the FDA's current shortage database rather than this article for the up-to-date status. Compounded products, when they are legally available, do not carry FDA approval for safety, efficacy, or sterility, and quality can vary meaningfully between compounding pharmacies. Anyone using a compounded version should discuss transitioning to a branded, FDA-approved product with their prescriber.

Insurance coverage for these drugs, particularly for weight management rather than diabetes, remains inconsistent and changes with payer policy. A patient's actual out-of-pocket cost and coverage status should be confirmed directly with their insurer rather than assumed from a list price, and list prices themselves change over time.

What is established, what is plausible, and what is not yet known

Established: Semaglutide and tirzepatide are both effective for weight loss compared with placebo in randomized trials; both require ongoing use to maintain results; both share a similar GI side-effect profile; semaglutide has trial-level cardiovascular outcome data in a defined high-risk population without diabetes.

Plausible but not proven at the individual level: That tirzepatide's larger average trial effect will translate into a proportionally larger benefit for any specific patient; that GLP-1 or dual-agonist therapy meaningfully treats sleep apnea or joint pain beyond the effect of weight loss itself; the durability of benefit far beyond the length of published trials.

Not established: Whether tirzepatide reduces major cardiovascular events the way semaglutide has been shown to in its own trial population, since that trial had not been published at the time this draft was prepared; long-term safety data beyond the multi-year windows already studied; how these drugs compare in a formal head-to-head randomized trial rather than across separate trials with different populations and time frames.

Frequently asked questions

References

1. Chao AM, et al. To Reenvision and Redefine: Considering the Role of Lifestyle Interventions in the New Era of Second-Generation Obesity Management Medications. 2026. https://pubmed.ncbi.nlm.nih.gov/42183911/
2. Incretin-Based Therapies in Obesity-Related Obstructive Sleep Apnea: A Narrative Review of Evidence Tiers and Mechanistic Plausibility. 2026. https://pubmed.ncbi.nlm.nih.gov/42591103/
3. GLP-1-Based Therapies in Pain Medicine: A Narrative Review and Expert Opinion on Obesity-Related Low Back and Knee Pain. 2026. https://pubmed.ncbi.nlm.nih.gov/42572056/

Other claims in this article reference well-known pivotal trials by name (STEP-1, STEP-2, SURMOUNT-1, SURMOUNT-2, SELECT) and FDA prescribing information for Wegovy and Zepbound. The specific numeric figures and citation links inherited from earlier drafting could not be independently verified during this revision and should be checked against the original NEJM, JAMA, and FDA label sources before this page is published.