Zepbound vs Wegovy: what the trials show, side by side

Zepbound and Wegovy at a glance

Zepbound and Wegovy are brand names. The medicine inside each one is what the trials tested, so this page uses both names. The tirzepatide page and the semaglutide page have the full details for each. Looking at the other brand pairs? Mounjaro vs Ozempic and Ozempic vs Wegovy cover them.

The mention of Wegovy HD reflects Novo Nordisk's March 2026 announcement. Check the official Wegovy HD label for its exact approved uses. See the brand and generic names page for how the products relate.

What did the head-to-head trial find?

One trial put the two medicines against each other. SURMOUNT-5 enrolled 751 adults with obesity who did not have type 2 diabetes and followed them for 72 weeks. Everyone took the highest dose they could tolerate of either tirzepatide or semaglutide. Because it was open label, participants and staff knew which drug was being used. There was no placebo group. Trials that compare other pairs of medicines are sorted on the combination and head-to-head trials page.

Source: SURMOUNT-5, published in the New England Journal of Medicine in 2025. These are group averages. The Atlas read the published abstract.

Why the SURMOUNT-5 result needs care

The gap is large, and it is the only direct comparison the Atlas found. It is still one trial, and a few details limit how far it reaches.

• Eli Lilly, which makes tirzepatide, funded it. Funding does not make a result wrong, and it is a reason to want other trials to agree.
• It was open label, which can affect how people report side effects and how they behave in a trial.
• The doses were not identical. Each person took the highest dose they could tolerate, so the two groups did not take matched amounts.
• The semaglutide group did not take the 7.2 mg strength that is now sold as Wegovy HD. The Atlas found no head-to-head trial against that strength.
• It enrolled adults without type 2 diabetes and lasted 72 weeks. It does not show what happens in other groups or over longer periods.

How do the placebo-controlled trials compare?

Each medicine also has its own large trial against placebo. These are the numbers that usually get set next to each other online. Do not line them up as if they were one experiment. The trials enrolled different people, ran for different lengths, used different analysis methods and were paid for by different companies. Only SURMOUNT-5 had both medicines in the same trial.

All three trials enrolled adults without diabetes and were funded by the maker of the medicine tested. STEP UP tested the 7.2 mg strength that Novo Nordisk sells as Wegovy HD. The trial results page charts these trials with their comparison groups, and the trial results explorer shows them in your own pounds.

How do the side effects compare?

Both labels list the same common side effects, and they are mostly digestive: nausea, diarrhea, vomiting, constipation and abdominal pain. Both list the same serious risks to know about, including pancreatitis, gallbladder problems, dehydration that can injure the kidneys, severe allergic reactions and, in people with type 2 diabetes, complications of diabetic retinopathy.

In SURMOUNT-5, digestive effects were the most common side effects in both groups. Most were mild to moderate and happened mainly while the dose was being raised. The week-by-week side effects page shows when they tend to appear. Both medicines carry a boxed warning about thyroid C-cell tumors seen in rodents and are not for people with a personal or family history of medullary thyroid carcinoma or MEN 2.

Does cost or coverage separate them?

It can. Insurance plans, Medicare programs and maker offers treat the two products differently, and the approved uses on each label can matter to a plan. Prices and offers change often, so this page lists none. The paying for GLP-1 medicines page covers the main ways people pay, and the cost tool adds up listed prices over a year.

Which one is right for me?

A trial average cannot answer that. The numbers in SURMOUNT-5 are group averages, and one person's result can be higher or lower. A prescriber looks at things the trials cannot, such as your health conditions, the other medicines you take, how you handle side effects, what your plan covers and what is in stock. Bring the questions below to the first visit.

If a pill is on your mind, the Wegovy pill is a daily tablet, and the weight-loss pills guide explains how pills compare with injections.

What about compounded versions of either one?

Compounded versions are made by pharmacies, are not FDA-approved and are not reviewed by the FDA for safety, effectiveness or quality before they are sold. The trial numbers on this page describe the approved products, not compounded ones. See compounded versus brand-name medicines and what semaglutide and tirzepatide are.

Quick answers

Is Zepbound better than Wegovy?

In SURMOUNT-5, adults with obesity and without type 2 diabetes lost an average of 20.2% on tirzepatide and 13.7% on semaglutide over 72 weeks. The trial was open label and funded by Eli Lilly. Which medicine is better for one person depends on their health, side effects, cost and coverage, which a prescriber can weigh.

How much weight do people lose on Zepbound compared with Wegovy?

SURMOUNT-5 is the head-to-head trial: an average of 20.2% on tirzepatide and 13.7% on semaglutide at 72 weeks. In separate placebo-controlled trials, tirzepatide produced averages of 15.0% to 20.9% (SURMOUNT-1) and semaglutide 2.4 mg produced 14.9% (STEP 1). Different trials should not be compared directly.

Do Zepbound and Wegovy work the same way?

Not exactly. Wegovy's semaglutide switches on the GLP-1 receptor. Zepbound's tirzepatide switches on both the GLP-1 and GIP receptors. Both are weekly injections that act on gut-hormone signals that affect appetite.

Are the side effects different?

Both labels list nausea, diarrhea, vomiting, constipation and abdominal pain as common. In SURMOUNT-5, digestive effects were the most common side effects in both groups and were mostly mild to moderate. Both carry a boxed warning about thyroid C-cell tumors seen in rodents.

What is Wegovy HD?

A higher-strength Wegovy injection. Novo Nordisk announced its U.S. approval in March 2026. In the STEP UP trial, adults who took semaglutide 7.2 mg weekly lost an average of 18.7% at 72 weeks, compared with 15.6% on 2.4 mg and 3.9% on placebo. The official Wegovy HD label lists what it is approved for.

Which one is approved for sleep apnea?

Zepbound is approved for moderate to severe obstructive sleep apnea in adults with obesity. The sleep apnea page explains the trials. Wegovy's label does not list sleep apnea.

Is there a Wegovy pill and a Zepbound pill?

The Wegovy pill is a daily semaglutide tablet approved for weight management. Zepbound is a weekly injection. A different pill medicine, orforglipron, is sold as Foundayo.

Are compounded versions the same as Zepbound and Wegovy?

No. Compounded drugs are made by pharmacies, are not FDA-approved and are not reviewed by the FDA for safety, effectiveness or quality before sale.

Can you switch from one to the other?

SURMOUNT-5 compared people who started on one medicine or the other, not people who switched. The switching page covers what the labels say and the small studies that exist.

Questions to ask

• Given my health history and the other medicines I take, how do Zepbound and Wegovy differ for me?
• What would each cost me with my coverage, including after the first month?
• Which side effects should I expect with each one, and when should I call?
• Do sleep apnea, heart disease or a liver condition change the choice for me?
• If the first medicine does not suit me, what is the plan?

What is still unknown

• The Atlas found one head-to-head trial in adults with obesity and without type 2 diabetes. It was open label and funded by the maker of tirzepatide, and the Atlas found no independent repeat of it.
• The Atlas found no head-to-head trial of tirzepatide against semaglutide 7.2 mg, the strength sold as Wegovy HD.
• How the two medicines compare beyond 72 weeks, or in other groups such as people with type 2 diabetes, is not shown by the trials on this page.
• The Atlas read the published abstracts of these trials, not the full papers, so it does not list side-effect rates for each group.
• Wegovy HD's approval comes from Novo Nordisk's announcement, so check the official label for its exact approved uses.