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Retatrutide vs. tirzepatide vs. semaglutide: how they compare

Updated October 30, 2026 · Wellness education, not medical advice

Side-by-side comparison

How they work differently

All three belong to the incretin family of medicines, which copy gut hormones released after you eat. Semaglutide activates only the GLP-1 receptor: it reduces appetite, slows stomach emptying and helps the pancreas release insulin when blood sugar is high. Tirzepatide adds activity at the GIP receptor, another post-meal hormone that improves insulin response and seems to make the combination more effective and, for some people, better tolerated than GLP-1 alone. Retatrutide adds a third target, the glucagon receptor. Glucagon increases energy expenditure and tells the liver to burn fat, so retatrutide doesn't only make people eat less — it may also make the body burn a bit more. This is the main reason researchers expected, and so far have seen, larger average weight loss with retatrutide, as well as particularly strong reductions in liver fat.

Retatrutide vs. tirzepatide (Mounjaro, Zepbound)

This is the comparison people search most, because both come from Eli Lilly and tirzepatide is already widely used. In its main obesity trial, SURMOUNT-1, tirzepatide 15 mg produced an average weight loss of about 20.9% over 72 weeks. Retatrutide 12 mg produced 28.3% over 80 weeks in TRIUMPH-1. On paper that's a large gap, but the trials enrolled somewhat different people, ran for different lengths of time and used slightly different analysis methods, so the numbers can't be compared directly — only a head-to-head trial can say how much better retatrutide really is for the same person. Side-effect profiles look broadly similar, dominated by nausea, diarrhea, constipation and vomiting. Retatrutide's rates of nausea and vomiting at its top dose were on the high side, and it caused more dysesthesia (tingling or burning skin sensations), which is uncommon with tirzepatide. The practical difference today is availability: tirzepatide can be prescribed, is covered by some insurance plans, and has years of real-world safety data; retatrutide can only be accessed in clinical trials.

Retatrutide vs. semaglutide (Ozempic, Wegovy)

Semaglutide 2.4 mg (Wegovy) produced an average weight loss of about 14.9% over 68 weeks in its STEP 1 trial, and the diabetes dose (Ozempic) produces less. Retatrutide's trial results are roughly double that. Semaglutide, however, has something retatrutide doesn't yet have: proof from the large SELECT trial that it reduces heart attacks, strokes and cardiovascular deaths in people with heart disease and overweight, plus approvals for kidney protection in type 2 diabetes. For someone whose main goal is protecting the heart, that evidence matters a great deal. Retatrutide's heart and kidney outcome trials are still running.

Which one is "best"?

There isn't a single best medicine. The choice depends on what is approved and available where you live, insurance and cost, your other conditions (heart disease, kidney disease, diabetes, fatty liver, sleep apnea), how much weight loss is medically needed, how you tolerate side effects, and your doctor's judgment. For many people a well-tolerated approved medicine taken consistently will do more good than waiting for a newer one. If retatrutide is approved — Lilly has said it plans to file with the FDA in the first quarter of 2027 — it will likely be one more option, possibly aimed at people who need larger weight loss or didn't reach their goals on other drugs. In the meantime, the only legitimate way to take retatrutide is through a clinical trial; see retatrutide approval status.

Side effects across all three

Because they share a mechanism, the three medicines share most side effects: nausea, vomiting, diarrhea, constipation, reflux and reduced appetite, usually worst during dose increases. All three can raise resting heart rate a few beats per minute, and all carry warnings or precautions about gallbladder disease, pancreatitis and use in pregnancy. Retatrutide adds dysesthesia to that list. Details are in retatrutide side effects.

Track what matters while you work on your weight. Whatever medicine or plan you and your doctor choose, the numbers that change first are often your resting heart rate, your blood pressure and your blood sugar. Cardivo measures heart rate and HRV from your fingertip on the iPhone camera in about 30 seconds — no Apple Watch needed — and keeps cuff blood pressure, glucose and mood in one ad-free journal, with weekly trends and a PDF you can bring to your appointments.

Frequently asked questions

Is retatrutide stronger than tirzepatide?

In separate trials retatrutide produced larger average weight loss (28.3% at 80 weeks on 12 mg) than tirzepatide (about 20.9% at 72 weeks on 15 mg), but there is no head-to-head trial yet, so a direct comparison isn't possible.

What is the difference between retatrutide and Mounjaro?

Mounjaro (tirzepatide) activates GIP and GLP-1 receptors and is approved. Retatrutide also activates the glucagon receptor and is still investigational.

Is retatrutide better than Ozempic?

Retatrutide led to roughly twice the average weight loss of semaglutide in separate trials, but semaglutide is approved, widely available, and has proven heart benefits that retatrutide has not yet shown.

Sources

• Eli Lilly — TRIUMPH-1 Phase 3 topline results (May 2026)
• Jastreboff et al., NEJM 2022 — Tirzepatide once weekly for obesity (SURMOUNT-1)
• Wilding et al., NEJM 2021 — Semaglutide 2.4 mg for obesity (STEP 1)
• Jastreboff et al., NEJM 2023 — Retatrutide phase 2 obesity trial

Cardivo is an ad-free iPhone app that reads heart rate and HRV from your fingertip on the camera in about 30 seconds — no Apple Watch needed — and keeps blood pressure, blood sugar, and mood in one journal you can share with your doctor as a PDF. Download on the App Store.

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