Tirzepatide vs. Semaglutide: How the Two GLP-1s Compare

The short answer on semaglutide vs tirzepatide is that both are weekly GLP-1-based injections with similar side effects, and tirzepatide has shown larger average weight loss in trials.

Semaglutide and tirzepatide share the same delivery, the same weekly cadence, and similar side effects. They differ in mechanism, and tirzepatide has shown larger average weight loss in trials, including the one head-to-head trial.

Semaglutide and tirzepatide both work through GLP-1, and the real difference is that tirzepatide adds a second target, GIP. Semaglutide and tirzepatide both mimic GLP-1, a gut hormone your body releases after eating that signals fullness, slows stomach emptying, and reduces appetite. That's the whole mechanism behind the reduced hunger people describe.

The difference is that tirzepatide adds a second target: GIP, another gut hormone involved in how your body handles food and energy. So semaglutide pulls one lever; tirzepatide pulls two. The leading theory is that engaging both pathways is why tirzepatide has tended to produce greater weight loss in studies — though “more receptors” doesn't automatically mean “better for you,” which is the part a physician weighs.

Semaglutide vs tirzepatide weight loss trials show more average weight loss with tirzepatide, including in the head-to-head trial. In the pivotal trials of the brand-name products:

• Semaglutide (in the STEP-1 trial) produced an average of about 15% body-weight reduction over 68 weeks, against 2.4% on placebo (Wilding et al., 2021).
• Tirzepatide (in the SURMOUNT-1 trial) produced an average reduction of about 21% over 72 weeks at the highest (15 mg) dose, against 3.1% on placebo (Jastreboff et al., 2022).
• Head to head (the SURMOUNT-5 trial), 751 adults with obesity but without type 2 diabetes took the maximum tolerated dose of one or the other for 72 weeks. Average weight change was -20.2% on tirzepatide and -13.7% on semaglutide, and the most common side effects in both groups were gastrointestinal and mostly mild to moderate (Aronne et al., 2025).

SURMOUNT-5 matters because it is the only one of the three that compared the two drugs directly; the first two figures come from separate trials against placebo. Two honest caveats you should hold onto. First, these are averages from controlled trials paired with lifestyle support — individual results vary a great deal, and they are not a guarantee of what any one person will experience. Second, these trials studied the FDA-approved brand products. That matters for the compounded-versus-brand distinction below.

Because these are averages, a slower start is common and usually has an ordinary explanation — we cover why you might not be losing weight on it separately, including how long the trials actually ran before reaching those figures.

You can apply these trial averages to your own weight with our GLP-1 weight loss calculator. It's an educational tool that shows the range of outcomes published in these trials, not a prediction of your own result and not a measure of whether treatment is appropriate for you.

On the evidence, tirzepatide tends to deliver more weight loss on average. That's a real point in its favor — but it's one input, not the whole decision.

Semaglutide and tirzepatide share a similar side-effect profile, and it's mostly gastrointestinal: nausea is the most common, along with things like diarrhea, constipation, and reduced appetite (which is partly the point). In the head-to-head trial, the most common adverse events in both groups were gastrointestinal, mostly mild to moderate, and occurred primarily during dose escalation (Aronne et al., 2025), which is why both are titrated up slowly.

Both also carry the same categories of more serious precautions, which is exactly why neither should be started without a physician evaluating your history first. Semaglutide and tirzepatide carry an FDA boxed warning about thyroid C-cell tumors seen in rodents, and both are contraindicated in people with a personal or family history of medullary thyroid carcinoma or with multiple endocrine neoplasia syndrome type 2 (MEN 2). Both labels also warn about acute pancreatitis, acute gallbladder disease, and acute kidney injury from dehydration (Wegovy label; Zepbound label). “Which has fewer side effects” isn't a clean win for either — they're comparable, and how you tolerate one specifically is individual.

Which of semaglutide or tirzepatide is right for you is not a question an article can answer, so be skeptical of any page that picks one for you sight unseen.

Tirzepatide's larger average weight loss makes it appealing, but the right choice genuinely depends on your health history, how you tolerate the medication, other conditions and medications, and a physician's judgment. Some people do very well on semaglutide; some tolerate one better than the other; candidacy and safety screening come first for both. The useful takeaway isn't “tirzepatide wins” — it's “these are two strong, closely related options, and which fits you is a medical decision.”

Before starting anywhere, it helps to understand your own baseline — you can check your BMI with our free BMI calculator and estimate your daily calorie needs with our calorie calculator. Which one is right for you is a medical decision, made with a physician.

Semaglutide and tirzepatide each exist as FDA-approved brand-name products (Ozempic® and Wegovy® for semaglutide; Mounjaro® and Zepbound® for tirzepatide). They also exist as compounded versions prepared by pharmacies.

Protocol MD provides physician-prescribed, compounded semaglutide and tirzepatide. Being direct about what that means: compounded medications are not FDA-approved, and a compounded version is not the same product as the brand-name medication that was studied in the trials above, even when it is made with the same active ingredient. We think it's important to state that plainly rather than blur the line. Whether a compounded option is appropriate for you is part of the conversation with a prescribing physician.

If you're considering either, the Protocol MD GLP-1 program starts the same way: a US-licensed physician reviews your intake and history and determines whether semaglutide, tirzepatide, or neither is appropriate for you. No medication is prescribed without that. It's physician-prescribed, not a marketplace, and candidacy and safety screening come first. Compounded GLP-1 (semaglutide and tirzepatide) is prescribed here as part of Protocol MD's broader physician-guided peptide therapy. If you want to see whether you're a fit, start with a quick evaluation.

The bottom line is that tirzepatide and semaglutide are close relatives (both GLP-1-based, both weekly, both working by reducing appetite), with one key mechanistic difference (tirzepatide's dual GIP/GLP-1 action) and a real evidence difference (greater average weight loss for tirzepatide in trials). But averages aren't individuals, side effects are comparable, and neither is right for everyone. The genuinely useful answer isn't a winner — it's that both are strong options, and which one fits you is a decision to make with a licensed physician after an evaluation, not from a comparison chart.