Head to head
Semaglutide
vs tirzepatide.
Two approved peptides with large trials behind them. One has the bigger average, and that is not the whole decision.
The short answer
On trial averages, tirzepatide wins. SURMOUNT-1 reported 20.9 percent mean body weight loss over 72 weeks at the top dose, while STEP 1 reported 14.9 percent over 68 weeks for semaglutide, and a randomized trial comparing the two directly for weight management reported greater loss on tirzepatide. That is as far as the data settles the argument.
The rest of the decision is not about effect size. It is about which drug your insurance covers, which one your stomach tolerates, what your medical history rules out, and which one you can actually get filled month after month. Physicians choose between these two on those grounds all the time, and the smaller average is frequently the right answer for a specific person.
| Semaglutide | Tirzepatide | |
|---|---|---|
| Mechanism | GLP-1 receptor agonist | Dual GIP and GLP-1 receptor agonist |
| Trial weight loss | 14.9 percent mean, 68 weeks, STEP 1 | 20.9 percent mean, 72 weeks, SURMOUNT-1 |
| Brand names | Ozempic, Wegovy, Rybelsus tablet | Mounjaro, Zepbound |
| Dosing | Weekly injection, 0.25 mg start, 2.4 mg target for weight | Weekly injection, 2.5 mg start, 5 to 15 mg maintenance |
| Side effects | Nausea, vomiting, diarrhea, constipation, reflux | Nausea, vomiting, diarrhea, constipation, indigestion |
| Monthly cost range | 1000 to 1350 dollars brand, less with savings programs | 1000 to 1350 dollars brand, less with savings programs |
| FDA status | Approved for diabetes and weight management | Approved for diabetes and weight management |
How they differ
Semaglutide activates one receptor, GLP-1, which slows stomach emptying, blunts appetite signaling and improves blood sugar control. Tirzepatide does that and adds activity at the GIP receptor, a second gut hormone pathway. The prevailing explanation for the larger average result is that hitting both pathways produces more appetite suppression and better metabolic effect than hitting one, and the trial numbers are consistent with that.
Everything else about the two is similar in daily life. Both are weekly subcutaneous injections, both start at a low dose and climb slowly to limit nausea, both carry the same boxed warning about thyroid C-cell tumors seen in rodents, and both are prescription-only in every form. Semaglutide has one advantage worth naming: it also exists as a daily tablet under the Rybelsus name, which matters to people who will not inject.
Which one the doctor picks
Insurance usually speaks first. A plan that covers one of these and not the other has effectively made the choice, and prior authorization rules differ between them and between diagnoses. Diabetes coverage is far easier to obtain than weight management coverage for either drug.
After that the reasoning is clinical. Someone with type 2 diabetes and a high starting weight is a natural candidate for the stronger dual agonist. Someone who struggled badly with nausea on a previous GLP-1 may do better on a gentler titration of semaglutide rather than more receptor activity. A patient already doing well on one drug is rarely moved for the sake of a better trial average. Family history of medullary thyroid carcinoma or multiple endocrine neoplasia type 2 rules out both. A history of pancreatitis or gallbladder disease changes the risk conversation for both.
Insurance and cost reality
Advertised brand pricing without insurance sits at roughly 1000 to 1350 dollars per month for both, and both manufacturers run savings programs and direct-to-patient options that often reduce that substantially. Where compounded programs remain lawful, telehealth clinics typically advertise 200 to 400 dollars per month for either molecule.
The compounding picture is the same for both. Large-scale compounding grew out of the FDA shortage listings, those shortages resolved, and through 2025 and 2026 the FDA moved to end most of that activity and acted against mass production and marketing of non-approved GLP-1 products. Narrow patient-specific compounding can still be lawful. If a program quotes a low price, the questions are which pharmacy, which license, and on what legal basis your prescription is being compounded.
Switching between them
Switching is routine and it is a physician decision, not a self-service one. The usual triggers are a weight loss plateau at a maximum tolerated dose, side effects that do not settle, a formulary change, or a supply problem at the pharmacy.
The mechanics matter. Doses do not convert between the two drugs, so a switch means starting the new medicine at its own starting dose and titrating up again, which usually brings back a few weeks of nausea. Expect a pause in progress during that period rather than a seamless handover, and expect the prescriber to want a check-in during the transition. Going the other direction, from tirzepatide down to semaglutide, follows the same rule for the same reason.
The safe path
Both drugs are prescription-only, and the visit that produces the prescription is what decides between them properly. A licensed physician reviews your history, weight, medications and labs, checks the contraindications, picks the medicine your coverage can actually sustain, and monitors the titration instead of leaving you to guess at dose increases.
Questions people ask
Which works better for weight loss?
Can you switch from semaglutide to tirzepatide?
Which one is cheaper?
Do they cause the same side effects?
Sources: NEJM — STEP 1 semaglutide · NEJM — SURMOUNT-1 tirzepatide · FDA on compounded GLP-1s · PubMed — head to head literature