THE SHORT ANSWER: All three are GLP-1-class medications used for medically supervised weight loss, but they’re not interchangeable. Semaglutide (Wegovy/Ozempic) and tirzepatide (Zepbound/Mounjaro) are both FDA-approved, with head-to-head data showing tirzepatide produces greater average weight loss (20.2% vs. 13.7% at 72 weeks in a direct trial). Retatrutide, a newer triple-agonist molecule, is still investigational, not yet FDA-approved, but its Phase 3 TRIUMPH-1 results showed up to 30.3% average weight loss at 104 weeks on the highest dose, the largest reduction reported for any GLP-1-class drug to date. Which one makes sense for you depends on your labs, history, and goals, not just the headline number.
The three medications, in plain terms
All three drugs work by mimicking gut hormones that regulate appetite and blood sugar, but they don’t all hit the same targets:
- Semaglutide activates the GLP-1 receptor only. It’s the most established of the three, with the longest real-world track record.
- Tirzepatide activates both GLP-1 and GIP receptors, a "dual agonist," which appears to be part of why it outperforms semaglutide in head-to-head data.
- Retatrutide goes a step further as a "triple agonist," activating GLP-1, GIP, and glucagon receptors. The added glucagon activity is thought to contribute to its larger effect size, though the mechanism is still being studied.
What the actual trial data shows
This is the part that matters more than marketing claims, so here are the numbers as reported in the primary trials:
Semaglutide vs. tirzepatide, head-to-head (SURMOUNT-5, published in NEJM): In a direct 72-week randomized trial of 751 adults with obesity, tirzepatide produced 20.2% average body weight loss compared to 13.7% with semaglutide, a statistically significant difference (p<0.001). Waist circumference dropped 18.4 cm with tirzepatide versus 13.0 cm with semaglutide. Tirzepatide also had a lower rate of GI-related treatment discontinuation (2.7% vs. 5.6%).
Tirzepatide alone (SURMOUNT-1, published in NEJM): In the original registration trial, tirzepatide achieved between 16.0% and 22.5% average weight loss depending on dose, in adults with obesity or overweight.
Retatrutide (TRIUMPH-1 Phase 3): At the highest studied dose (12 mg), participants averaged 28.3% weight loss at 80 weeks and 30.3% at 104 weeks. About 45.3% of people on the 12 mg dose lost 30% or more of their body weight, a range that starts to approach outcomes historically associated with bariatric surgery. Side effects followed a similar pattern to the other two drugs (nausea, diarrhea, constipation, vomiting), with discontinuation due to adverse events ranging from 4.1% at the lowest dose to 11.3% at the highest.
The honest caveat: these numbers come from different trials, different populations, and different follow-up windows. This is not a single apples-to-apples study of all three drugs at once. Cross-trial comparisons like this are useful for understanding general trends, not for predicting your individual result.
The regulatory status difference matters as much as the numbers
This is the detail that gets glossed over in a lot of the content circulating on this topic right now:
- Semaglutide is FDA-approved for chronic weight management (Wegovy) and type 2 diabetes (Ozempic).
- Tirzepatide is FDA-approved for chronic weight management (Zepbound) and type 2 diabetes (Mounjaro).
- Retatrutide is not yet FDA-approved for any use. It remains an investigational compound, available through compounding pharmacies by prescription, with Phase 3 trial data published but no completed FDA review or approval as of this writing.
That doesn’t mean retatrutide isn’t a legitimate, closely-tracked option. The trial data above is real and substantial, but "investigational" is a meaningfully different regulatory category than "FDA-approved," and anyone considering it should understand that distinction clearly before starting.
How we approach this at Vitality Dartmouth
Peptide and GLP-1 protocols are a core part of what we do, and our functional wellness approach leans toward retatrutide when a client is a good candidate for it. The trial data on efficacy is compelling, and we prescribe it directly as a functional wellness clinic. But the choice isn’t automatic:
- Labs and history come first, every time, through the same intake process we use for genomic testing, not a one-size-fits-all prescription.
- We disclose investigational status plainly. If retatrutide is a fit for you, you’ll hear directly from us that it’s not yet FDA-approved, exactly as we do for every client who asks.
- FDA-approved options are always on the table. Semaglutide and tirzepatide remain appropriate, well-established choices for many clients, and we prescribe those too when they’re the better fit.
- This isn’t a standalone decision. Whichever medication makes sense fits into a broader plan: nutrition, training load, and monitoring, through our coaching programs.
Frequently asked questions
Which one is "best"?
There isn’t a universal answer. Tirzepatide has outperformed semaglutide in head-to-head data, and retatrutide’s Phase 3 numbers are the largest reported so far, but "best on average in a trial" and "right for your labs and history" aren’t the same question. That’s a conversation, not a lookup table.
Is retatrutide legal?
Yes. It is available by prescription through licensed providers and compounding pharmacies, the same channel through which we prescribe it at Vitality Dartmouth. "Investigational" refers to its FDA approval status, not its legal availability.
Can I switch between them?
Sometimes, depending on your history and response. This is exactly the kind of decision that should go through a provider tracking your labs and progress, not a self-directed switch.
Do you offer GLP-1 medications near me?
Yes. Vitality Dartmouth is based in Dartmouth, MA and works with clients across the SouthCoast, including New Bedford, Westport, Fairhaven, and Fall River, with RN-supervised protocols built around your labs and history.
The bottom line
Semaglutide, tirzepatide, and retatrutide are not just different brand names for the same drug. They are three distinct molecules with different receptor targets, different regulatory status, and meaningfully different trial results. The right starting point isn’t picking the biggest number you’ve seen online; it’s an honest conversation about your labs, your history, and what each option’s approval status actually means for you.
This article is for educational purposes only and is not medical advice. Retatrutide is an investigational compound and is not FDA-approved; it should be discussed with a licensed provider who can explain its regulatory status and evidence base. Individual results vary, and cross-trial comparisons cannot predict individual outcomes. Discuss any treatment decision with a licensed healthcare provider.