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See if you qualify →If you have spent any time on the weight-loss internet, you have seen these four names. Often in the same sentence, often used interchangeably. They are not interchangeable — but the confusion is understandable, because behind four brand names there are really only two drugs.
This guide is the explainer we wish existed when we were first fielding these questions in clinic. It covers what each drug is, what it does, how they perform side-by-side in real trials, what the experience actually feels like week to week, what they cost in 2026, and where compounded semaglutide and tirzepatide fit in now that the FDA shortage period is over.
What are Ozempic, Wegovy, Mounjaro, and Zepbound, really?
All four are injectable peptide medicines in the GLP-1 class. They mimic gut hormones your body already makes after you eat. Those hormones tell your pancreas to release insulin, tell your stomach to empty more slowly, and tell your brain you are satisfied — which is why hunger drops, portions feel smaller, and the constant background chatter about food gets quieter.
Two of them (Ozempic, Wegovy) contain semaglutide. The other two (Mounjaro, Zepbound) contain tirzepatide, which is a so-called "dual agonist" because it activates both the GLP-1 receptor and the GIP receptor. That extra receptor is the main reason tirzepatide tends to produce more weight loss.
| Brand | Active ingredient | FDA-approved for | Manufacturer | Form |
|---|---|---|---|---|
| Ozempic | Semaglutide | Type 2 diabetes | Novo Nordisk | Once-weekly injection |
| Wegovy | Semaglutide | Chronic weight management (BMI ≥ 30, or ≥ 27 with a weight-related condition) | Novo Nordisk | Once-weekly injection |
| Mounjaro | Tirzepatide | Type 2 diabetes | Eli Lilly | Once-weekly injection |
| Zepbound | Tirzepatide | Chronic weight management (same BMI criteria as Wegovy) | Eli Lilly | Once-weekly injection |
How is semaglutide different from tirzepatide?
Semaglutide activates one receptor: GLP-1. Tirzepatide activates two: GLP-1 and GIP (glucose-dependent insulinotropic polypeptide). GIP is another gut hormone released after meals. Activating both seems to produce a bigger effect on appetite, insulin sensitivity, and fat storage than activating GLP-1 alone.
This matters in two places: efficacy (discussed below) and side effects (slightly different pattern). It does not really change dosing — both are weekly injections, both escalate over ~4–5 months from a starter dose to a target dose.
Dose ladders (simplified)
| Week | Semaglutide (Ozempic / Wegovy) | Tirzepatide (Mounjaro / Zepbound) |
|---|---|---|
| 1–4 | 0.25 mg | 2.5 mg |
| 5–8 | 0.5 mg | 5 mg |
| 9–12 | 1.0 mg | 7.5 mg |
| 13–16 | 1.7 mg (Wegovy) / stay at 1 mg (Ozempic) | 10 mg |
| 17–20 | 2.4 mg (Wegovy target) | 12.5 mg |
| 21+ | — | 15 mg (Zepbound max) |
Which one causes more weight loss?
The most-cited numbers come from the STEP trials for semaglutide and the SURMOUNT trials for tirzepatide. These are large, randomized, placebo-controlled trials in people with obesity but without diabetes.
| Trial | Drug | Duration | Mean weight loss at max dose |
|---|---|---|---|
| STEP 1 (2021) | Semaglutide 2.4 mg | 68 weeks | ~14.9% of body weight |
| SURMOUNT-1 (2022) | Tirzepatide 15 mg | 72 weeks | ~20.9% of body weight |
| SURMOUNT-5 (2025) | Tirzepatide 15 mg vs. semaglutide 2.4 mg (head-to-head) | 72 weeks | Tirzepatide: ~20.2% · Semaglutide: ~13.7% |
So, yes — on average, tirzepatide gets more weight off than semaglutide. But "on average" is doing a lot of work there. In any given trial, the middle 50% of responders sit within a fairly wide band, and some people do better on semaglutide than on tirzepatide. We have watched both things happen in the same clinic in the same week.
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How do side effects compare?
Both drugs have the same core side-effect picture because both hit the GLP-1 receptor. Nausea, constipation, diarrhea, reflux, and early satiety are common in the first 4–8 weeks and usually ease after a dose has been held steady for a few weeks.
The practical differences:
- Nausea tends to be slightly more common on semaglutide at equivalent weight-loss levels.
- Diarrhea tends to be slightly more common on tirzepatide, while constipation is more common on semaglutide.
- Severity of any side effect tracks more with how fast you escalate the dose than with which molecule you use. Going slow is almost always the right answer.
- Rare but serious: both carry warnings for pancreatitis, gallbladder disease, and — in people with a personal or family history of medullary thyroid carcinoma or MEN-2 — thyroid C-cell tumors (from rodent studies; contraindicated).
For a full side-effect playbook including how to manage nausea, timing tricks, and when to actually call your clinician, see GLP-1 Side Effects Decoded.
What about cardiovascular and metabolic benefits?
GLP-1s do more than change the number on the scale. At minimum, both drugs lower HbA1c, blood pressure, and triglycerides in most patients. Beyond that:
- Semaglutide has the strongest cardiovascular outcomes dataset so far. The SELECT trial (2023) showed a 20% reduction in major adverse cardiovascular events in people with obesity and pre-existing cardiovascular disease.
- Tirzepatide has trials in progress (SURPASS-CVOT, SURMOUNT-MMO) but does not yet have a completed cardiovascular outcomes trial of the same scale.
- Both drugs have sleep-apnea and MASLD (fatty liver) data showing meaningful improvement, though tirzepatide's MASLD data is more mature as of 2026.
What do they cost in 2026 — and is insurance covering any of this?
Cash list prices for the branded pens have been broadly stable since 2024:
| Brand | Approx. cash list price (US, 2026) | Typical insurance outcome |
|---|---|---|
| Ozempic | $1,000/month | Usually covered for type 2 diabetes with prior authorization. Rarely covered for weight loss alone. |
| Wegovy | $1,350/month | Covered by some employer plans; increasingly excluded from commercial formularies in 2025–26. Medicare covers it only for specific CV indications (post-Nov 2024 rule update). |
| Mounjaro | $1,060/month | Similar to Ozempic — covered for T2D, rarely for weight loss. |
| Zepbound | $1,060/month (vial form lower) | Similar to Wegovy. Lilly Direct self-pay vials opened up access at a lower price point in 2024 and those prices have held. |
If you have good weight-loss coverage, use it. If you do not — and most people do not — you have three realistic options:
- 1Manufacturer direct (Lilly Direct vials for Zepbound). Lower than list price, limited dose range, self-pay only.
- 2Compounded semaglutide or tirzepatide from a licensed U.S. 503A or 503B pharmacy. $200–$400/month typical. Legal in specific situations even after the FDA "shortage resolved" declaration — see Compounded GLP-1 in 2026 for the nuance.
- 3Stopping, which is the most expensive option in the long run because weight tends to return quickly when the medication stops. Most patients we see decide that the cheaper ongoing option — whichever it is — beats the off-and-on pattern.
How should I actually choose between them?
In clinic, the decision tree usually looks like this:
- 1Do you have type 2 diabetes? If yes, we start with the indicated drug (Ozempic or Mounjaro) because insurance coverage is dramatically better and the co-pay may be near zero.
- 2Do you have known cardiovascular disease or high 10-year ASCVD risk? If yes, semaglutide gets a strong look because of SELECT trial evidence.
- 3Is maximum weight loss the priority (e.g., pre-surgery, severe metabolic disease, high BMI)? Tirzepatide has the higher ceiling.
- 4Is cost a hard constraint? Then we're often looking at compounded semaglutide or tirzepatide, and the discussion shifts to pharmacy quality, not brand.
- 5Have you tried one before and hated it? That's a real signal. Switching molecules sometimes solves a tolerability problem, but sometimes the same person does better with a slower titration on the original drug.
Frequently asked questions
No. Ozempic is only FDA-approved for type 2 diabetes. When it is prescribed specifically for weight loss, that is off-label. Wegovy is the same molecule (semaglutide) with FDA approval for weight management.
Yes, and this is common. Your clinician will usually start you at the equivalent or a slightly lower tirzepatide dose and re-escalate. Expect a brief re-adjustment period with mild nausea or digestive changes.
Individual results vary more than the drug does. In group averages, tirzepatide trends slightly better for nausea and slightly worse for loose stools. Titration speed is the biggest variable either way.
Most people regain a significant portion of lost weight within a year of stopping (the STEP-4 extension showed ~two-thirds of weight returning by week 120 after discontinuation). That is why these are usually thought of as long-term medications, like a statin or a blood-pressure drug, not a 6-month intervention.
Rybelsus is oral semaglutide approved for type 2 diabetes. It is less effective for weight loss than the injectable forms at currently-approved doses, and absorption is finicky (has to be taken on an empty stomach, with very little water). Oral tirzepatide is in trials but not FDA-approved for anything as of April 2026.
You don't need to, but people who build in a protein target (~1g per pound of goal body weight), resistance training 2–3x/week, and 7+ hours of sleep consistently see better long-term results and preserve more muscle mass. GLP-1s work whether or not you do those things — they just work better when you do.
The active molecule is the same. The manufacturing context is different: branded Ozempic is made by Novo Nordisk and FDA-approved as a finished product; compounded semaglutide is prepared by a licensed U.S. pharmacy from API. Quality depends heavily on the pharmacy. We cover this in depth in our compounded GLP-1 guide.
No. Both manufacturers advise discontinuing at least 2 months (semaglutide) and ~1 month (tirzepatide) before attempting pregnancy. Talk to your clinician about timing if this applies to you.
Bottom line
Ozempic and Wegovy are the same drug (semaglutide) with different labels. Mounjaro and Zepbound are the same drug (tirzepatide) with different labels. Tirzepatide gets more weight off on average; semaglutide has stronger cardiovascular outcomes data. Side effects overlap heavily and are mostly driven by titration speed. Price is the dominant real-world variable, and compounded versions from licensed U.S. pharmacies have become the practical path for most cash-paying patients.
The right drug is the one a clinician chooses with you — based on your metabolic history, your tolerability, and what you can actually sustain for years. That is the conversation we try to have in clinic every day.
References
- 1.Wilding JPH, et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity. N Engl J Med. 2021;384:989-1002 (STEP 1).
- 2.Jastreboff AM, et al. Tirzepatide Once Weekly for the Treatment of Obesity. N Engl J Med. 2022;387:205-216 (SURMOUNT-1).
- 3.Aronne LJ, et al. Tirzepatide vs Semaglutide in Adults with Obesity (SURMOUNT-5). N Engl J Med. 2025.
- 4.Lincoff AM, et al. Semaglutide and Cardiovascular Outcomes in Obesity without Diabetes (SELECT). N Engl J Med. 2023;389:2221-2232.
- 5.FDA Prescribing Information: Wegovy (semaglutide), updated 2024.
- 6.FDA Prescribing Information: Zepbound (tirzepatide), updated 2024.
About this article
Dr. Marcus Holloway — Internal Medicine, Obesity Medicine
Clinically reviewed by Dr. Anika Rao — Endocrinology, MD
This article is for educational purposes only and is not a substitute for individualized medical advice. Talk to a licensed clinician before starting, stopping, or changing any prescription.
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