Semaglutide vs. Tirzepatide: How the Two GLP-1 Drugs Actually Differ

Semaglutide (sold as Ozempic, Wegovy and Rybelsus) and tirzepatide (sold as Mounjaro and Zepbound) are both FDA-approved prescription drugs that copy hormones your gut releases after you eat, which turns down appetite and helps control blood sugar. The core difference is that semaglutide switches on one of those hormone signals, called GLP-1, while tirzepatide switches on two: GLP-1 and a second one called GIP.

In the one head-to-head weight-loss trial so far, which tirzepatide’s maker paid for, people on tirzepatide lost more weight on average, and an earlier head-to-head trial in type 2 diabetes pointed the same way. Semaglutide has the longer track record and more approved uses.

So when people search “tirzepatide vs. semaglutide,” the honest answer isn’t “one wins.” It’s a trade-off, and this page lays out each side, the evidence strength and who paid for it.

The short answer

Semaglutide is FDA-approved, marketed as Ozempic, Wegovy and Rybelsus; tirzepatide is FDA-approved, marketed as Mounjaro and Zepbound, as of October 2026. Compounded versions of either are not FDA-approved.

Here’s the comparison at a glance.

If you’re new to this whole drug family, our explainer on what peptides are covers the basics. Both drugs are peptides, meaning short chains of the same building blocks that make up proteins.

Which brand is which

Most confusion here comes from the names. There are five brands but only two drugs.

The same molecule under different brands means different approved uses, not different drugs. Ozempic and Wegovy are both semaglutide, labeled for different conditions; our Wegovy vs. Ozempic page explains that split. Likewise, Mounjaro and Zepbound are the same drug, one labeled for type 2 diabetes and the other for weight management and sleep apnea.

How they work: one signal vs. two

Both drugs work on receptors, which are the “locks” on your cells that a hormone fits into to deliver its message.

Semaglutide fits one lock: the receptor for GLP-1, a hormone your gut releases after a meal that tells your brain you’re full and tells your pancreas to release insulin. It also slows how fast your stomach empties, which is part of why you feel full longer.

Tirzepatide fits that same lock, plus a second one. That second lock belongs to GIP, short for glucose-dependent insulinotropic polypeptide, which is another after-meal gut hormone that also nudges insulin release. The current Mounjaro label describes the drug as working on both the GIP and GLP-1 receptors (Mounjaro prescribing information, Aug 2026).

Why would two signals matter? The leading explanation is that hitting both hormone pathways at once adds up to a stronger effect on appetite and blood sugar than hitting one. That’s a reasonable explanation for the trial results below, but it’s not a proven cause. Researchers are still working out exactly what the GIP half contributes.

Tirzepatide vs. semaglutide for weight loss: what the trials show

On average, tirzepatide produced more weight loss than semaglutide in both direct comparison trials, and a large real-world study points the same way.

The head-to-head trial (SURMOUNT-5). This study randomly assigned 751 adults with obesity, and without diabetes, to either tirzepatide or semaglutide for 72 weeks. People on tirzepatide lost an average of 20.2% of their body weight, compared with 13.7% on semaglutide (Aronne et al., NEJM 2025).

Two details matter. First, Eli Lilly, which makes tirzepatide, funded the trial. Second, it was open-label, meaning both the participants and their doctors knew which drug each person was taking (Lilly, May 11, 2025). Open-label designs are common in comparisons of drugs given in different ways, but they’re a step below “blinded” trials, where nobody knows who got what.

An earlier head-to-head trial, in diabetes (SURPASS-2). This 40-week, open-label trial randomly assigned 1,879 adults with type 2 diabetes to one of three tirzepatide strengths or to semaglutide at the highest strength then approved for diabetes. Every tirzepatide group had larger drops in blood sugar and body weight (Frías et al., NEJM 2021). Lilly funded this one too, and semaglutide is now also sold at higher strengths than that trial tested, such as Wegovy HD.

The real-world check. The result isn’t resting on one company’s trials alone. A 2024 study in JAMA Internal Medicine, by researchers at the health-data company Truveta rather than either drugmaker, looked at the medical records of more than 18,000 matched adults with overweight or obesity (Rodriguez et al., JAMA Internal Medicine 2024). People on tirzepatide lost more weight at 3, 6 and 12 months, and were more likely to hit 5%, 10% and 15% weight-loss milestones.

That study was observational, meaning it tracked people who were already prescribed one drug or the other instead of randomly assigning them, so it can’t fully rule out other differences between the groups. Still, a randomized trial and a large real-world study pointing in the same direction is more convincing than either one alone.

Lilly’s newer, indirect comparison. On Sept 29, 2026, Lilly announced an analysis suggesting Zepbound was associated with more weight loss than Wegovy HD, the higher-strength version of Wegovy (Lilly, Sept 29, 2026).

Read that one with care. It was not a head-to-head trial. It was an indirect comparison, meaning Lilly statistically compared results from two separate trials (its own SURMOUNT-1 and Novo Nordisk’s STEP UP), with adjustments for differences between the groups. Lilly reported a statistically significant advantage under one way of measuring the results, but under a second way, the differences were smaller and not statistically significant. Lilly’s own release acknowledges there’s no head-to-head trial of these two products, so treat it as a useful signal, not settled proof.

Bottom line: the weight-loss evidence favors tirzepatide on average, and it comes from more than one kind of study. “On average” is doing real work in that sentence. Individual results vary, and many people lose substantial weight on semaglutide too.

Side effects: mostly the same, and the dropout data cut both ways

The two drugs share the same main side effects, and those are mostly stomach-related: nausea, diarrhea, vomiting, constipation and stomach pain. In SURMOUNT-5, side effects on both drugs were mostly stomach-related and generally mild to moderate (Lilly, May 11, 2025).

Both also carry the same boxed warning, which is the FDA’s strongest label warning, for the risk of thyroid C-cell tumors, a type of thyroid tumor seen in rodent studies; the labels say it’s unknown whether the drugs cause these tumors in people (Ozempic prescribing information; Mounjaro prescribing information; Drugs@FDA: Wegovy).

Where the trials differ is on quitting. In SURMOUNT-5, fewer people stopped tirzepatide because of side effects. About 6.1% of people on tirzepatide quit the trial due to side effects, compared with 8.0% on semaglutide (Lilly, May 11, 2025). That’s a modest gap, and it covers quitting for any side effect, not stomach effects alone. The diabetes trial, SURPASS-2, went the other way: 6.0% to 8.5% of people quit tirzepatide over side effects, depending on strength, versus 4.1% on semaglutide (Frías et al., NEJM 2021). The real-world JAMA Internal Medicine study found stomach-related side effects were similar between the two groups (Rodriguez et al., 2024).

So which is safer? There’s no single winner. Both drugs have similar warning lists, and which one is the better fit depends on a person’s own health history, which is a conversation for a prescriber. The official FDA labels, linked above, are the most complete place to see each drug’s full list of warnings.

Muscle loss: do you lose more on one than the other?

We didn’t find any head-to-head study that measured muscle loss on semaglutide versus tirzepatide. So the honest answer to “which one costs you more muscle” is that, as far as we found, it hasn’t been directly tested.

What does exist is single-drug data. When you lose weight by any method, part of what you lose is lean mass, which means everything that isn’t fat: muscle, but also water, organs and bone.

In a substudy of the SURMOUNT-1 trial that used body scans, about three-quarters of the weight people lost on tirzepatide was fat, and about a quarter was lean mass. That’s the same split seen in the placebo group, who lost less weight without the drug, and it held across subgroups such as age and sex (Look et al., Diabetes Obes Metab 2025, doi:10.1111/dom.16275). The study was sponsored by Lilly, and its authors include Lilly employees.

That finding is reassuring for tirzepatide on its own terms: the drug didn’t shift weight loss toward lean mass compared with losing weight without it. But it doesn’t tell you whether semaglutide does better or worse, because the semaglutide trials measured body composition separately, in different people, and we haven’t verified those figures against the primary paper for this page.

Heart, kidney and other approved uses

This is where semaglutide still has the edge on breadth. Here’s what each drug is FDA-approved for, by brand, as of October 2026.

The biggest recent change is on the tirzepatide side. On Aug 27, 2026, the FDA approved Mounjaro to lower the risk of major heart events in adults with type 2 diabetes who are at high risk for them (Mounjaro prescribing information). That puts it level with semaglutide on heart protection in type 2 diabetes, where Ozempic and Rybelsus already carry similar approvals (Ozempic prescribing information; Rybelsus prescribing information).

It doesn’t erase semaglutide’s lead on breadth. Semaglutide (as Wegovy) is approved to lower heart risk in people with heart disease and obesity or overweight who don’t have diabetes, and tirzepatide has no matching approval as of October 2026. Semaglutide also holds the kidney approval (Ozempic) and the MASH liver approval (Wegovy). Tirzepatide holds the sleep apnea approval (Zepbound).

Why a prescriber might choose semaglutide instead

Given tirzepatide’s weight-loss numbers, people often ask why a doctor would prescribe semaglutide at all. There are several fact-based reasons, and none of them is a recommendation for you specifically.

• The approved use fits the person. Someone with heart disease and obesity but no diabetes, or someone with diabetes and kidney disease, matches an approved semaglutide use that tirzepatide doesn’t currently have.
• A pill is an option. Semaglutide comes as a tablet (Wegovy tablets and Rybelsus). Tirzepatide is injection-only as of October 2026.
• A longer track record. Semaglutide has been on the market since Ozempic’s approval in December 2017, about four and a half years before Mounjaro in May 2022 (Drugs@FDA 209637; Drugs@FDA 215866). More years on the market means more real-world experience with its side effects.
• How the person tolerates it. Someone already doing well on semaglutide may have no reason to change.
• Insurance coverage. A plan may cover one drug and not the other, which can decide the question on its own.

Pills vs. shots

If you’d rather not inject, semaglutide is currently the only one of the two that comes as a pill. The FDA approved Wegovy tablets on Dec 22, 2025, for weight reduction and heart-risk reduction (FDA approval letter), and Rybelsus is a semaglutide pill for type 2 diabetes that, since October 2025, is also approved to lower heart risk in high-risk adults with type 2 diabetes (Rybelsus prescribing information). Our semaglutide page covers Wegovy tablets and Wegovy HD in more detail.

Tirzepatide is injection-only as of October 2026. Lilly’s own GLP-1 pill is a different molecule, not tirzepatide, so it isn’t part of this comparison.

Cost and insurance

This section is information, not advice. We haven’t verified current prices, so we’re not listing them here.

There are three main ways people pay for either drug:

• Insurance. Coverage depends heavily on the plan and on the reason for the prescription. Weight-management coverage is far from universal: in 2025, 19% of employers with 200 or more workers covered GLP-1 drugs for weight loss in their largest plan (KFF, 2025).
• The manufacturers’ self-pay programs. Both Lilly and Novo Nordisk run programs that sell their branded, FDA-approved products directly to people with a valid prescription. You still need a prescription, and the cost is still significant.
• Manufacturer savings cards and coupons. These can lower out-of-pocket costs for eligible people, usually those with commercial insurance. Terms change often.

Compounded versions and where you can actually get each drug

Both brand-name drugs are FDA-approved prescription medicines, so there’s a clear, legitimate route: a prescription from a licensed provider, filled at a licensed pharmacy. Here’s what each channel does and doesn’t guarantee.

A prescription filled at a licensed pharmacy. This gets you the branded product, made in FDA-inspected facilities, with an official label and a prescriber accountable for the decision. It doesn’t guarantee your insurance will pay for it.

The manufacturers’ self-pay programs. Same branded, FDA-approved product, prescription still required. It’s an alternative to insurance, not a discount guarantee.

Telehealth clinics. Many are real medical practices where a licensed provider writes a real prescription after an online visit. But some supply compounded versions instead of the brand-name drug; in March 2026 the FDA sent warning letters to 30 telehealth companies whose marketing implied their compounded products were the same as approved drugs (FDA, Mar 3, 2026). So ask which one you’re getting.

Compounding pharmacies. A compounded drug is one a pharmacy mixes itself instead of buying it from the manufacturer. Compounded semaglutide and tirzepatide are not FDA-approved, and the FDA notes that approved drugs go through its review for safety, effectiveness and quality while compounded drugs don’t (FDA compounding statement, updated Apr 1, 2026).

During the shortages of 2022 to 2025, the FDA let pharmacies make broad copies of these drugs. Those shortages are over: tirzepatide’s was resolved in December 2024 and semaglutide’s in February 2025, and the FDA’s grace periods for compounders ended in 2025. Today, a traditional compounding pharmacy can generally make these drugs only in narrow circumstances, such as when a prescriber documents that a specific patient needs a meaningfully different version (FDA). On Apr 30, 2026, the FDA also proposed formally excluding semaglutide and tirzepatide from the list of ingredients that larger “outsourcing facility” compounders can use; as of October 2026, the FDA page shows no final decision (FDA announcement). Our regulatory tracker follows that decision.

The compounding industry argues the FDA is drawing the line in the wrong place. The Alliance for Pharmacy Compounding, which is the compounding industry’s own trade group and so has a direct financial stake, told the FDA in February 2026 that licensed compounders prepare drugs only on individual prescriptions, source ingredients through FDA-registered and inspected channels, and shouldn’t be lumped in with gray-market sellers, adding that counterfeits sold through bogus websites are the real danger; it asked for risk-based enforcement (APC letter to FDA, Feb 9, 2026).

That argument is fair on one point: a licensed pharmacy, where a pharmacist is accountable for what’s in the vial, is genuinely different from an anonymous website. But it doesn’t change the basic facts. Compounded versions still aren’t FDA-reviewed for safety, effectiveness or quality, and the broad shortage-era pathway has ended.

“Research use only” websites. These sites sell semaglutide or tirzepatide directly to anyone, with no prescription, labeled “not for human use.” They guarantee nothing: no prescriber, no oversight, and no check that the product is what it claims or contains the stated amount. The FDA has warned about products made with different chemical forms of semaglutide than the approved drug, and about counterfeit Ozempic (see our semaglutide page for the FDA warnings). Being able to buy something online doesn’t make it safe or legal to use.

Related reading

• Semaglutide: the full profile, including Wegovy tablets and Wegovy HD
• Tirzepatide: including how Mounjaro and Zepbound differ
• Other GLP-1 drugs in our GLP-1 and weight-loss hub
• Retatrutide, still in trials, which works on three hormone signals

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