Retatrutide vs Zepbound vs Wegovy: how do they compare?

Dr. Linda's take

Patients bring me screenshots of retatrutide headlines more often than you might expect, usually with the same question underneath: is this something I could take instead of Zepbound or Wegovy? The honest answer starts with a distinction that gets lost in a lot of online content: Zepbound and Wegovy are FDA-approved medications you can actually be prescribed today, while retatrutide is an investigational drug still working through clinical trials, with no FDA approval and no availability outside of research settings. This piece compares what the published research shows about all three, side by side, without pretending they are three interchangeable options sitting on the same shelf.

Key takeaways

At a glance

| | Retatrutide | Zepbound (tirzepatide) | Wegovy (semaglutide) |
|---|---|---|---|
| FDA approval status | Not FDA-approved; investigational | FDA-approved for chronic weight management | FDA-approved for chronic weight management |
| Available by prescription | No | Yes | Yes |
| Receptors targeted | GIP, GLP-1, and glucagon | GIP and GLP-1 | GLP-1 only |
| Maker | Eli Lilly | Eli Lilly | Novo Nordisk |
| Dosing studied/approved | Weekly injection, doses up to 12 mg studied in phase 2 | Weekly injection, up to 15 mg | Weekly injection, up to 2.4 mg |
| Headline trial | Phase 2 (Jastreboff et al, 2023) | Phase 3 SURMOUNT-1 (Jastreboff et al, 2022) | Phase 3 STEP 1 (Wilding et al, 2021) |
| Average weight loss at highest studied dose | 24.2% at 48 weeks (12 mg, phase 2) | 20.9% at 72 weeks (15 mg) | 14.9% at 68 weeks (2.4 mg) |

How does each medication work?

Wegovy's active ingredient, semaglutide, is a GLP-1 receptor agonist. It is indicated in combination with a reduced calorie diet and increased physical activity to reduce excess body weight and maintain weight reduction long term in adults with obesity, and in adults with overweight in the presence of at least one weight-related comorbid condition, and it is also approved to reduce the risk of major cardiovascular events in adults with established cardiovascular disease and either obesity or overweight.

Zepbound's active ingredient, tirzepatide, is a dual GIP and GLP-1 receptor agonist, meaning it activates two hormone receptors instead of one. Zepbound is indicated in combination with a reduced-calorie diet and increased physical activity to reduce excess body weight and maintain weight reduction long term in adults with obesity or adults with overweight in the presence of at least one weight-related comorbid condition, and it is also indicated to treat moderate to severe obstructive sleep apnea in adults with obesity.

Retatrutide goes a step further mechanistically: it is designed as a triple agonist, activating the GIP, GLP-1, and glucagon receptors together. The added glucagon receptor activity is thought to increase energy expenditure and promote fat breakdown on top of the appetite-related effects shared with the other two receptors. Retatrutide is not currently approved by the FDA and is considered an investigational medication, so this mechanism, however promising in early research, has not yet been reviewed and approved by regulators for real-world use.

What have the clinical trials shown?

Wegovy's approval rested on the STEP program. In the STEP 1 trial, a 68-week, double-blind, placebo-controlled study of adults with obesity, semaglutide 2.4 mg produced a mean body weight change of -14.9% compared with -2.4% with placebo.

Zepbound's approval rested on the SURMOUNT program. In the SURMOUNT-1 trial, a 72-week, double-blind, randomized, controlled trial of adults with obesity, tirzepatide produced mean weight reductions of 15.0% at 5 mg, 19.5% at 10 mg, and 20.9% at 15 mg, compared with 3.1% with placebo.

Retatrutide's only substantial published data so far comes from a single phase 2 trial: a 48-week, randomized, double-blind, placebo-controlled trial of 338 adults with obesity, testing doses of 1 mg, 4 mg, 8 mg, and 12 mg. At the 12 mg dose, participants lost an average of 24.2% of body weight at 48 weeks, compared with about 2.1% in the placebo group. The 8 mg group lost an average of 22.8%, and the 4 mg group lost an average of 17.1%, at the same 48-week mark. Those numbers are notable, and they are also a single, smaller, earlier-stage trial result. Eli Lilly has since moved retatrutide into phase 3 testing under a program called TRIUMPH, and larger, longer trials are what will determine whether the phase 2 magnitude holds up, along with the full safety picture regulators would need before any approval decision.

What do the safety profiles look like?

Zepbound and Wegovy both carry an FDA boxed warning: in animal studies, both tirzepatide and semaglutide caused thyroid C-cell tumors, and whether either drug causes the same in humans is not known. Because of that finding, both medications are contraindicated for anyone with a personal or family history of medullary thyroid carcinoma or Multiple Endocrine Neoplasia syndrome type 2. In their respective phase 3 trials, the most common adverse events for both drugs were gastrointestinal, including nausea, vomiting, and diarrhea, typically mild to moderate and more common during dose escalation.

Retatrutide's safety data is limited to what the phase 2 trial has shown so far: the most common adverse events reported were gastrointestinal, including nausea, vomiting, and diarrhea, and these were dose-related and mostly mild to moderate in severity. Because retatrutide has not completed the full regulatory review process, its long-term safety profile is not yet fully characterized the way an FDA-approved drug's is, and no finalized prescribing label exists for it.

Is retatrutide available, and should you look for it?

No. Retatrutide is not FDA-approved and is not available by prescription, through a pharmacy, or through a compounding pharmacy, regardless of what an ad or a social post implies. If you see retatrutide offered for sale, that is not an FDA-approved medication being dispensed under the oversight that applies to Zepbound or Wegovy. Zepbound and Wegovy, by contrast, are approved options you can actually discuss with a licensed clinician today.

What should you ask your clinician?

If you want a structured way to start that conversation about the options available today, Body Good Studio's quiz is built to map your history to a starting point before you talk with a clinician.

Frequently asked questions

Is retatrutide better than Zepbound or Wegovy?

We do not know yet. Retatrutide's only substantial data comes from one 48-week phase 2 trial, while Zepbound and Wegovy have full phase 3 programs and years of real-world FDA-approved use behind them. A head-to-head comparison will need retatrutide's completed phase 3 results and, eventually, an approved label to be a fair one.

Can a doctor prescribe retatrutide instead of Zepbound or Wegovy?

No. Retatrutide is not FDA-approved, so it cannot legally be prescribed for general use. Zepbound and Wegovy can be prescribed by a licensed clinician for their approved indications.

Why does retatrutide show larger weight loss numbers in headlines?

Retatrutide's phase 2 trial reported a 24.2% average weight loss at the 12 mg dose over 48 weeks, which is a larger figure than the 20.9% and 14.9% averages reported in Zepbound's and Wegovy's respective phase 3 trials. Phase 2 trials are smaller and earlier-stage than phase 3 trials, so this comparison is preliminary, not a settled result.

What is the main mechanistic difference between the three?

Wegovy's semaglutide targets one receptor, GLP-1. Zepbound's tirzepatide targets two, GIP and GLP-1. Retatrutide is being studied as a triple agonist targeting GIP, GLP-1, and glucagon receptors together.

Do Zepbound and Wegovy have the same safety warnings?

Both carry the same FDA boxed warning about thyroid C-cell tumors seen in animal studies, and both are contraindicated for anyone with a personal or family history of medullary thyroid carcinoma or Multiple Endocrine Neoplasia syndrome type 2. Beyond that shared warning, always review each medication's own full prescribing information with your clinician, since they are separate FDA-approved products.

References

1. Jastreboff AM, Kaplan LM, Frías JP, et al (2023). Triple-Hormone-Receptor Agonist Retatrutide for Obesity - A Phase 2 Trial. New England Journal of Medicine, via PubMed (National Library of Medicine). https://pubmed.ncbi.nlm.nih.gov/37366315/ (Accessed 2026-07-12).
2. Jastreboff AM, Aronne LJ, Ahmad NN, et al (2022). Tirzepatide Once Weekly for the Treatment of Obesity. New England Journal of Medicine, via PubMed (National Library of Medicine). https://pubmed.ncbi.nlm.nih.gov/35658024/ (Accessed 2026-07-12).
3. Wilding JPH, Batterham RL, Calanna S, et al (2021). Once-Weekly Semaglutide in Adults with Overweight or Obesity. New England Journal of Medicine, via PubMed (National Library of Medicine). https://pubmed.ncbi.nlm.nih.gov/33567185/ (Accessed 2026-07-12).
4. U.S. Food and Drug Administration / Eli Lilly (2024). ZEPBOUND (tirzepatide) injection, for subcutaneous use - Prescribing Information. DailyMed, National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=487cd7e7-434c-4925-99fa-aa80b1cc776b (Accessed 2026-07-12).
5. U.S. Food and Drug Administration / Novo Nordisk (2025). WEGOVY (semaglutide) injection, for subcutaneous use - Prescribing Information. DailyMed, National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=f5e548d0-cc79-4c34-a3f5-e20a5b8b6564 (Accessed 2026-07-12).
6. Eli Lilly and Company (2026). What to know about retatrutide. Lilly.com. https://www.lilly.com/news/stories/what-to-know-about-retatrutide (Accessed 2026-07-12).
7. Alkhezi OS, Alahmed AA, Alfayez OM, Almutairi AR, Almohaini HS, Ahmed W (2024). The "Weight" for a New Agent Is Almost Over: A Commentary on the Novel Triagonist Retatrutide for Obesity. Diabetes, Obesity and Metabolism, via PMC (National Library of Medicine). https://pmc.ncbi.nlm.nih.gov/articles/PMC11536522/ (Accessed 2026-07-12).