Semaglutide vs. Tirzepatide: Head-to-Head on Weight Loss, Side Effects, and Cost

Semaglutide and tirzepatide are the two GLP-1 medications almost everyone is choosing between. They're related but not identical, and the "better" one genuinely depends on your goal, your tolerance for side effects, and your budget. Here's a measured, head-to-head comparison grounded in the pivotal trials — including the first study that put the two molecules directly against each other for weight loss. Any prices mentioned reflect the published pricing of the providers we track (last reviewed 2026).

If you are not choosing but already on one of them, that is a different question with a different answer — the dose does not carry across. See switching from semaglutide to tirzepatide.

Two molecules, two mechanisms

Both are once-weekly injections that curb appetite and slow gastric emptying, but they don't work through the same machinery. Semaglutide — the molecule in Wegovy (and, at diabetes doses, Ozempic) — is a single-target GLP-1 receptor agonist⁵. Tirzepatide — the molecule in Zepbound (and, at diabetes doses, Mounjaro) — is a dual agonist that activates two gut-hormone receptors, GIP and GLP-1⁶. If the four brand names feel like a lot to track, our brand-name decoder untangles which pairs are actually the same drug. That second mechanism is a large part of why tirzepatide's average results in trials have tended to run higher. It's also why the two can feel different from person to person; more receptor activity is not automatically "better" for everyone.

What the pivotal trials showed

Each molecule earned its approval on a large phase 3 program. In STEP-1, once-weekly semaglutide 2.4 mg produced about 15% average body-weight loss over 68 weeks in adults with overweight or obesity, versus roughly 2.4% on placebo¹. In SURMOUNT-1, tirzepatide reached about 21% average loss at its 15 mg dose over 72 weeks, with the lower doses landing a few points behind². Read separately, both are dramatic results by the standards of anti-obesity medicine — but separate trials with different participants can't be compared one-to-one, which is why the head-to-head studies matter so much.

The head-to-head data

There are now two direct comparisons. SURPASS-2 pitted the two against each other in adults with type 2 diabetes and found tirzepatide led to greater reductions in A1C and body weight than semaglutide across its doses³. That was suggestive, but it was a diabetes trial with lower semaglutide doses than the weight-management version.

The more decisive evidence is SURMOUNT-5, the first head-to-head trial in adults with obesity but without diabetes, using the higher weight-management doses of both drugs. At 72 weeks, tirzepatide produced about 20% average weight loss versus about 14% for semaglutide — a clear edge for the dual agonist in a fair fight⁴. Notably, gastrointestinal side effects severe enough to stop treatment were somewhat less common on tirzepatide than on semaglutide in that trial⁴. So on the averages, tirzepatide comes out ahead on both efficacy and, in this study, tolerability — but averages describe groups, not the person reading this.

Side effects and tolerability

Both molecules share the same side-effect family: nausea, diarrhea, constipation, and vomiting, concentrated in the early weeks and around each dose increase. For most people these are manageable and fade, and a slow, patient titration schedule usually matters more than which molecule you picked. SURMOUNT-5's edge for tirzepatide on treatment-stopping GI events is real but modest, and it doesn't override individual experience — plenty of people tolerate semaglutide beautifully and struggle on tirzepatide, or the reverse. If side effects are your main worry, that's a conversation to have with your prescriber about dose and pace, not a reason to assume one molecule is universally gentler.

Cost and telehealth pricing

Cost often breaks the tie. Semaglutide is usually the lower-priced option, especially in compounded form, and it's the more widely stocked of the two. Across the telehealth providers we track, compounded semaglutide commonly runs about $90–$250 a month, while compounded tirzepatide runs higher, roughly $145–$350 a month (last reviewed 2026). Some providers charge the same flat price for either molecule, which quietly makes tirzepatide the better value on their plan, while others price tirzepatide at a real premium. Our top-ranked pick, for example, offers both on one account. If cost is shaping your decision, the compounded vs brand-name guide explains the underlying price gap, and the comparison hub lines up each provider's semaglutide and tirzepatide pricing side by side.

Which molecule fits you

Reach for tirzepatide if your priority is the highest average weight loss, the head-to-head data speaks to you, and the higher price works for your budget over the long run. Lean semaglutide if you want a proven, widely available, usually cheaper option and are comfortable with strong-but-slightly-lower average results — it also has the longer real-world track record, an FDA-approved cardiovascular risk-reduction indication that tirzepatide doesn't currently carry (see GLP-1s and heart health), and, in oral form, a needle-free route (see injections vs oral or sublingual). Because a GLP-1 is typically a multi-year commitment, weigh the ongoing cost, not the first-month rate — our long-term provider guide covers why.

Whichever you choose, confirm your provider actually carries it and check the real maintenance price. Still torn? The 2-minute quiz folds molecule preference, budget, and support into our honest Match Score and surfaces providers that carry your pick — including a single-price option like Found that charges the same for either molecule. Or start with our top-ranked match below.

On the tirzepatide side, the escalation schedule and where it is reasonable to stop climbing are covered in every step from 2.5 mg to 15 mg.