The GLP-1 medication class has reshaped medical weight loss faster than any drug category in modern memory. Two molecules dominate the conversation in 2026: semaglutide, sold as Wegovy for weight loss and Ozempic for type 2 diabetes, and tirzepatide, sold as Zepbound for weight loss and Mounjaro for diabetes. Both are FDA-approved. Both are effective. But they are not the same drug, and the differences matter when you are choosing between them.
Here is a clear, side-by-side comparison.
What they are
Semaglutide is a GLP-1 receptor agonist. It mimics a single hormone — glucagon-like peptide-1 — that the body naturally releases after eating. It signals fullness, slows stomach emptying, and reduces appetite.
Tirzepatide is a dual GLP-1 and GIP receptor agonist. It mimics two hormones — GLP-1 plus glucose-dependent insulinotropic polypeptide. The dual mechanism appears to drive both stronger appetite suppression and better insulin response than GLP-1 alone.
Both are once-weekly subcutaneous injections.
Head-to-head efficacy
The clinical data is the cleanest place to compare them. In the SURMOUNT-1 trial of tirzepatide for weight loss, patients on the highest dose lost an average of 22.5 percent of body weight over 72 weeks. In the STEP 1 trial of semaglutide for weight loss, patients on the highest dose lost an average of 14.9 percent of body weight over 68 weeks.
A direct head-to-head trial (SURMOUNT-5) published in 2025 compared the two medications in adults with obesity over 72 weeks. Tirzepatide produced an average weight loss of approximately 20 percent versus approximately 14 percent for semaglutide — a meaningful gap on the same patient population.
For most patients seeking significant weight loss, tirzepatide produces more weight loss on average. Individual results vary, and some patients respond better to semaglutide than the trial averages suggest.
Side effect profile
Both medications share the same general side effect categories — gastrointestinal effects driven by slower stomach emptying. The most common are nausea, vomiting, diarrhea, constipation, and reflux. These tend to be worst during dose escalation and improve as the body adjusts.
In trial data, the side effect rates between the two medications are broadly similar, with some patients tolerating one better than the other. Tirzepatide's GIP component may offer a slight nausea advantage in some patients, but this is not consistent across all data.
Less common but more serious risks for both classes include pancreatitis, gallbladder disease, and a boxed warning for thyroid C-cell tumors (based on rodent data; the clinical relevance in humans remains debated). Both are contraindicated in patients with a personal or family history of medullary thyroid carcinoma or MEN 2 syndrome.
Cost in 2026
This is where the comparison gets complicated.
Brand-name pricing without insurance:
•Wegovy (semaglutide): roughly $1,300 per month at list price
•Zepbound (tirzepatide): roughly $1,060 per month at list price
•Ozempic and Mounjaro (the diabetes versions): similar list pricing, generally not covered for weight loss alone
With insurance, coverage is highly variable. Many commercial plans cover GLP-1s for patients with a BMI over 30 or over 27 with comorbidities. Medicare currently does not cover GLP-1s for weight loss.
Compounded versions:
•Compounded semaglutide: typically $250 to $500 per month
•Compounded tirzepatide: typically $400 to $650 per month
Compounded versions are produced by licensed compounding pharmacies and are legal under FDA shortage rules — but the FDA has periodically removed both molecules from the official shortage list, which restricts compounding eligibility. The compounded market in 2026 remains in flux. Always verify your provider is sourcing from a state-licensed compounding pharmacy with legitimate access.
Manufacturer savings programs through Eli Lilly (Zepbound) and Novo Nordisk (Wegovy) can substantially reduce out-of-pocket cost for patients who qualify.
Dosing schedules
Both medications start at low doses and escalate over several months to minimize side effects.
Semaglutide weight-loss dosing (Wegovy):
•Weeks 1 through 4: 0.25 mg weekly
•Weeks 5 through 8: 0.5 mg weekly
•Weeks 9 through 12: 1.0 mg weekly
•Weeks 13 through 16: 1.7 mg weekly
•Week 17 onward: 2.4 mg weekly (target dose)
Tirzepatide dosing (Zepbound):
•Weeks 1 through 4: 2.5 mg weekly
•Weeks 5 onward: 5 mg, 7.5 mg, 10 mg, 12.5 mg, or 15 mg weekly depending on response and tolerance
The slow escalation matters. Patients who try to push the dose too quickly typically have worse side effects with no faster weight loss.
How to choose
For most patients with significant weight to lose and no specific reason to prefer one over the other, the data favors tirzepatide on average weight-loss results. For patients who tolerate one medication poorly, switching to the other is reasonable and often productive.
A few practical guidelines:
•If insurance covers one and not the other, start with the covered medication
•If you are paying out of pocket and can access either, tirzepatide is likely the better starting choice based on efficacy
•If you have a personal history of severe nausea or GI issues, discuss gradual escalation with your provider regardless of which medication you choose
•If a previous attempt with one medication failed due to side effects or lack of response, the other is worth considering before giving up on the class
What both medications require
Neither medication is a substitute for sustained lifestyle change. The patients who maintain weight loss after stopping either drug are almost universally those who built durable habits around nutrition, sleep, strength training, and protein intake while on the medication. Patients who relied on the medication alone tend to regain a substantial portion of lost weight within a year of discontinuation.
The medication works. But the medication is the easy part. The harder work is building the eating and movement patterns that hold the result in place when the prescription ends.
Finding a provider
Look for a provider with training in obesity medicine. American Board of Obesity Medicine (ABOM) certification indicates specialized training in this area. Endocrinologists and primary care physicians with weight management experience are also good options. Avoid "weight loss clinics" that promote either medication aggressively without taking a full medical history, monitoring labs, or providing nutritional counseling.
A reputable provider will discuss both medications, explain the trade-offs, and help you choose based on your medical history, insurance, budget, and goals — not based on which one they happen to stock.
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