Semaglutide vs Tirzepatide: Which GLP-1 Is Right for You?

The short answer: tirzepatide produces more weight loss on average. In the first trial to compare the two drugs directly, people on tirzepatide lost 20.2% of their body weight over 72 weeks, against 13.7% on semaglutide. Semaglutide is still a genuinely effective medication with a longer track record and a lower price, and for a lot of people it is the better starting point. The right choice depends on how much weight you are trying to lose, how your body handles the first few months, and what you want to spend.

The two drugs work differently

Both medications imitate hormones your gut already releases after a meal. Those hormones slow how fast your stomach empties, tell your brain you are full, and steady your blood sugar. The practical effect is the one patients describe most often: the constant background chatter about food gets quiet.

Semaglutide targets one of those hormone pathways, GLP-1. It is the active ingredient in Ozempic® and Wegovy®, and it is the molecule most of the public associates with this category.

Tirzepatide targets two, GLP-1 and GIP. It is the active ingredient in Mounjaro® and Zepbound®. Adding the second pathway appears to improve how the body handles fat and sugar on top of the appetite effect, which is the leading explanation for the gap in results.

What the head-to-head trial actually found

Until recently the comparison was guesswork, because the two drugs had only been tested against placebo in separate trials with different participants. SURMOUNT-5, published in the New England Journal of Medicine in July 2025, put them against each other: adults with obesity and without type 2 diabetes, randomly assigned to the maximum tolerated dose of one drug or the other, once weekly for 72 weeks.

Two things stand out. The first is the size of the gap: 6.5 percentage points of body weight, which for a 220 pound starting weight is roughly 14 pounds of difference. The second is that tirzepatide did not buy that result with worse tolerability. Fewer people quit tirzepatide over digestive side effects than quit semaglutide.

Side by side

Do the side effects differ?

Not by much, and not in the way most people expect. Both drugs cause the same family of digestive side effects: nausea, constipation, diarrhea, and reflux, concentrated in the first weeks and around each dose increase. Both are titrated the same way, starting at a low dose and stepping up slowly so your body adapts.

The trial data slightly favors tirzepatide on tolerability, with fewer participants discontinuing over digestive symptoms. In practice the bigger variable is not which molecule you take, it is how patiently the dose is increased. We cover the full picture in GLP-1 side effects: what to expect and how to get ahead of them.

How to choose

A provider makes this call with your full health history in front of them, but these are the patterns that come up most:

• Start with semaglutide if your goal is in the 20 to 40 pound range, you have never taken a GLP-1, or the monthly cost is the deciding factor. It is effective, well understood, and the cheaper entry point.
• Start with tirzepatide if you are aiming to lose 50 pounds or more, your BMI is 35 or higher, or you want the strongest option available and the cost works for you.
• Switch to tirzepatide if you have been on semaglutide at a full dose for several months and your weight has genuinely plateaued rather than just slowed.
• Let tolerability decide if you have a sensitive stomach. Either drug can be restarted at a lower dose, and a slower climb usually solves more than a change of molecule.

Whichever you choose is not a one-way door. Dose and medication both get adjusted over time as your body changes, which is the entire point of having a provider rather than a subscription box.

Injection, tablet, or pen?

Both molecules come in three formats here, and the format is a separate decision from the molecule. The weekly vial is the most economical. The prefilled pen removes the measuring step: you dial your dose and inject. The daily tablet removes needles altogether, with some trade-offs we go through in oral GLP-1 vs injection.

Getting started

Eligibility generally starts at a BMI of 27 or higher, or 25 or higher with a weight-related condition such as high blood pressure, prediabetes, or sleep apnea. Our 2-minute eligibility quiz checks that and suggests which molecule fits your goal, and a US-licensed provider reviews your history before anything is prescribed. You can also compare all six treatments on the treatments page.