# Retatrutide: Side Effects, Results, and FDA Approval Status

Source: https://www.dietglp.com/blog/retatrutide-guide/
Published: 2026-10-18
Keywords: retatrutide, retatrutide side effects, retatrutide weight loss, retatrutide fda approval, is retatrutide fda approved, retatrutide vs tirzepatide, retatrutide vs zepbound, retatrutide when will it be available, is retatrutide safe, retatrutide eli lilly, retatrutide brand name, retatrutide cost, how retatrutide works, retatrutide compounded

**TL;DR:** Retatrutide is an experimental once-a-week shot from Eli Lilly that acts on three hormone receptors: GLP-1, GIP and glucagon. In the TRIUMPH-1 trial, people on the top 12 mg dose lost 28.3% of their body weight on average over 80 weeks, but it is not FDA approved and Lilly plans to file for approval in early 2027. Anything sold as retatrutide today outside a trial is unapproved, and the FDA has received reports of deaths after people used such products. Whatever you take now, protein and strength work protect your muscle, and [Sharpy](https://apps.apple.com/us/app/glp-diet-app-sharpy/id6762084138) turns both into one simple daily plan.

What is retatrutide, does it work, and can you get it yet? Here is the short answer. **Retatrutide is an experimental weight loss shot from Eli Lilly, taken once a week.** It is the first drug to act on three hormone receptors at once: GLP-1, GIP and glucagon. In its biggest trial so far, people on the top dose lost about 28% of their body weight over 80 weeks. But it is **not FDA approved**, and Lilly does not plan to ask the FDA for approval until early 2027.

Retatrutide is in the news this week for a worrying reason. Reports published October 14 and 15, 2026 say the FDA has received reports of deaths after people used products sold as retatrutide outside of trials. Lilly's CEO also called it a key next drug for the company. So more people are asking what it is and whether it is safe.

This guide sticks to what Lilly's trial results and regulators actually say.

---

## What is retatrutide and how does it work?

Most weight loss shots work on one or two gut hormones:

- **Semaglutide** (Ozempic, Wegovy) acts on the GLP-1 receptor.
- **Tirzepatide** (Mounjaro, Zepbound) acts on GLP-1 and GIP. Our [GLP-1 vs GIP guide](/blog/glp1-vs-gip-explained/) explains that pair.
- **Retatrutide** adds a third: the **glucagon** receptor.

GLP-1 and GIP turn down hunger and slow how fast your stomach empties. Glucagon is thought to raise the energy your body burns and help it use stored fat. That is why people call retatrutide a "triple agonist" or "triple G." In the trials it was given as a shot under the skin once a week, starting at 2 mg and raised every 4 weeks to the target dose.

**Does retatrutide have a brand name?** Not yet. Lilly gives a drug its brand name close to approval. Any "brand" you see on a vial sold online is not a Lilly product.

## Retatrutide weight loss results: the phase 3 trials

Lilly has reported several phase 3 trials, called TRIUMPH. The biggest is **TRIUMPH-1**: 2,339 adults with obesity, or overweight plus a weight-related health problem, and no diabetes. They started at an average of 248.5 pounds.

Here is the average weight loss at 80 weeks, from Lilly's May 21, 2026 announcement (people who stayed on the drug):

| Dose | Weight lost | Pounds lost | Lost 30% or more |
|---|---|---|---|
| Placebo | 2.2% | 5.5 lb | 0.5% of people |
| 4 mg | 19.0% | 47.2 lb | 15.3% of people |
| 9 mg | 25.9% | 64.4 lb | 37.9% of people |
| 12 mg | 28.3% | 70.3 lb | 45.3% of people |

When Lilly counted everyone, including people who stopped the drug, the top dose averaged **25.0%**. In a longer extension of people who started with a BMI of 35 or more, those who stayed on the top doses averaged about **30%** weight loss at 104 weeks.

Other trials showed lower but still large numbers:

- **TRIUMPH-2** (people with type 2 diabetes): about 21% on the top dose at 80 weeks.
- **TRIUMPH-3** (people with heart disease): about 23% on the top dose at 80 weeks.
- **TRIUMPH-4** (people with knee osteoarthritis): 28.7% on 12 mg at 68 weeks, with big drops in knee pain.

People with diabetes usually lose less weight on these drugs, so the lower TRIUMPH-2 number was expected.

## Retatrutide side effects

Retatrutide's side effects look like those of other GLP-1 drugs, but more frequent at the higher doses. Here are the most common ones in TRIUMPH-1:

| Side effect | 4 mg | 9 mg | 12 mg | Placebo |
|---|---|---|---|---|
| Nausea | 28.6% | 38.4% | 42.4% | 14.8% |
| Diarrhea | 25.2% | 34.1% | 32.0% | 13.5% |
| Constipation | 23.8% | 25.9% | 26.1% | 10.9% |
| Vomiting | 10.6% | 22.8% | 25.3% | 4.8% |
| Dysesthesia (odd skin feeling) | 5.1% | 12.3% | 12.5% | 0.9% |
| Stopped due to side effects | 4.1% | 6.9% | 11.3% | 4.9% |

**Dysesthesia** is the one people search most. It means skin that tingles, burns or feels unusual to touch. Lilly says it was mostly mild to moderate, most cases went away during treatment, and most people kept taking the drug.

These numbers come from a controlled trial with doctors watching closely and slow dose increases. They do not tell you what happens with an unknown product bought online. If you have stomach trouble on an approved GLP-1 today, our [nausea guide](/blog/managing-nausea-on-ozempic/) can help.

## Retatrutide vs tirzepatide (Zepbound) and semaglutide (Wegovy)

These drugs have not been tested against each other in a finished trial. The table puts their main obesity trials side by side, counting everyone who started.

| | Retatrutide 12 mg | Tirzepatide 15 mg (Zepbound) | Semaglutide 2.4 mg (Wegovy) |
|---|---|---|---|
| Receptors | GLP-1, GIP, glucagon | GLP-1, GIP | GLP-1 |
| Main trial | TRIUMPH-1, 80 weeks | SURMOUNT-1, 72 weeks | STEP 1, 68 weeks |
| Average weight loss | 25.0% | 20.9% | 14.9% |
| How it is taken | Weekly shot | Weekly shot | Weekly shot or daily pill |
| FDA approved | No | Yes | Yes |

The trials were different lengths and enrolled different people, so treat this as a rough guide. For the approved options, see our [GLP-1 medication comparison](/blog/glp1-medication-comparison/). Lilly's new daily pill is covered in our [Foundayo guide](/blog/foundayo-orforglipron-guide/).

## Bigger weight loss means a bigger muscle question

Losing 25% to 30% of your body weight is a lot of weight to lose. When you eat much less, your body can lose muscle along with fat unless you give it a reason to keep it. That is true on any GLP-1 drug, and it will matter even more with stronger drugs.

Two habits protect muscle:

1. **Hit a daily protein target.** Our guide on [how much protein you need on a GLP-1](/blog/protein-target-on-glp1/) shows how to find your number.
2. **Lift 2 to 3 times a week.** Start simple with [resistance training on GLP-1](/blog/resistance-training-on-glp1/).

[Sharpy](https://apps.apple.com/us/app/glp-diet-app-sharpy/id6762084138) is built for exactly this. It gives you one protein target, one 20-minute workout and one Shape Score a day, so you can see whether you are losing fat and keeping muscle on whatever medicine your doctor prescribes.

## When will retatrutide be FDA approved?

No one knows yet. Here is the timeline so far:

| Date | Event |
|---|---|
| June 2023 | Phase 2 results in NEJM: up to 24.2% weight loss at 48 weeks |
| December 11, 2025 | TRIUMPH-4 (knee osteoarthritis) results |
| May 21, 2026 | TRIUMPH-1 results: 28.3% on 12 mg at 80 weeks |
| July 23, 2026 | TRIUMPH-2 and TRIUMPH-3 results; Lilly says it will file with the FDA in Q1 2027 |
| October 2026 | Not yet submitted; not approved anywhere |

Lilly earlier said it might file in 2026. It told CNBC it needed more time to collect manufacturing and quality data. After a filing, the FDA review takes months. There is no announced price either, so "retatrutide cost" figures online are not from Lilly.

## Is black-market retatrutide safe?

This is the question in this week's news. Because the trial results are so strong, some websites, med spas and clinics are selling products labeled retatrutide. Here is what is known:

- **It is not legal to sell.** Lilly says retatrutide is legally available only in its trials. The FDA told state boards in March 2025 that compounding pharmacies cannot use retatrutide because it is not approved.
- **Reports of harm are rising.** The Atlanta Journal-Constitution reported on October 15, 2026 that the FDA has received more than 70 adverse event reports tied to retatrutide since 2024, including four deaths this year. CBS News first reported two of the death reports. These reports are not verified and do not prove the product caused the harm, and no one knows what was really in the vials.
- **Lilly is suing sellers.** Lilly has filed lawsuits against online sellers, a compounding pharmacy, a weight loss clinic and med spas, and warns these products may contain the wrong dose, the wrong drug or contaminants.

Our [compounded GLP-1 guide](/blog/compounded-glp1/) explains why unapproved versions are risky. If you want retatrutide, the safe path is a clinical trial. Ask your doctor or search ClinicalTrials.gov.

## The bottom line

Retatrutide produced some of the largest weight loss ever seen in a drug trial. It also caused more stomach side effects at higher doses, and it is still at least many months from any possible approval. Until then, the approved drugs are the safe choice, and decisions about them belong to you and your prescriber.

On any of these drugs, the job is the same: lose fat, keep muscle. [Sharpy](https://apps.apple.com/us/app/glp-diet-app-sharpy/id6762084138) puts your protein, your 20-minute workout and your Shape Score in one place on your iPhone.

---

## Sources

- [Lilly's triple agonist, retatrutide, delivered powerful weight loss in pivotal Phase 3 obesity trial, Eli Lilly, May 21, 2026](https://www.prnewswire.com/news-releases/lillys-triple-agonist-retatrutide-delivered-powerful-weight-loss-in-pivotal-phase-3-obesity-trial-302778859.html)
- [Retatrutide results presented at ADA 2026, Eli Lilly, June 6, 2026](https://www.prnewswire.com/news-releases/lillys-triple-agonist-retatrutide-drove-substantial-improvements-in-weight-a1c-knee-osteoarthritis-pain-and-obstructive-sleep-apnea-demonstrating-its-remarkable-potential-to-treat-obesity-and-its-complications-302793169.html)
- [Lilly, with new data, to seek FDA approval of retatrutide, BioPharma Dive, July 23, 2026](https://www.biopharmadive.com/news/lilly-retatrutide-fda-application-obesity-drug-results/825987/)
- [Triple-hormone-receptor agonist retatrutide for obesity: a phase 2 trial, NEJM, 2023](https://www.nejm.org/doi/full/10.1056/NEJMoa2301972)
- [Tirzepatide once weekly for the treatment of obesity (SURMOUNT-1), NEJM, 2022](https://www.nejm.org/doi/full/10.1056/NEJMoa2206038)
- [Once-weekly semaglutide in adults with overweight or obesity (STEP 1), NEJM, 2021](https://www.nejm.org/doi/full/10.1056/NEJMoa2032183)
- [Knockoff versions of this unapproved weight-loss drug are being openly sold in Georgia, AJC, October 15, 2026](https://www.ajc.com/news/2026/10/knockoff-versions-of-this-unapproved-weight-loss-drug-are-being-openly-sold-in-georgia/)
- [The black market for retatrutide may already be turning deadly, Gizmodo, October 14, 2026](https://gizmodo.com/the-most-powerful-weight-loss-drug-yet-isnt-approved-but-its-black-market-may-already-be-turning-deadly-2000825769)

## Frequently asked questions

**Q: Is retatrutide FDA approved?**

A: No. As of October 2026, retatrutide is not approved by the FDA or any other regulator. Lilly says it plans to submit it to the FDA in the first quarter of 2027. Lilly states that retatrutide is legally available only to people in its clinical trials.

**Q: When will retatrutide be available?**

A: Not before the FDA reviews it. Lilly plans to file in early 2027, and an FDA review usually takes many months after that. No approval date or launch date has been announced, so any date you see online is a guess.

**Q: How much weight do people lose on retatrutide?**

A: In TRIUMPH-1, adults with obesity and no diabetes lost 19.0%, 25.9% and 28.3% of their body weight on average at the 4 mg, 9 mg and 12 mg doses over 80 weeks, versus 2.2% on placebo. In people with type 2 diabetes (TRIUMPH-2), weight loss was lower, about 21% on the top dose.

**Q: What are the side effects of retatrutide?**

A: In TRIUMPH-1 the most common side effects were nausea, diarrhea, constipation and vomiting. Up to 42% of people on the top dose had nausea. Some people also had dysesthesia, an odd or uncomfortable skin sensation, which Lilly says was mostly mild and often went away. About 11% of people on the 12 mg dose stopped because of side effects.

**Q: Is retatrutide better than tirzepatide (Zepbound)?**

A: The two have not been compared head to head in a finished trial. In separate trials, retatrutide 12 mg produced more average weight loss than tirzepatide 15 mg did in its main obesity trial, but the studies were different in length and people. Retatrutide also had higher rates of stomach side effects. Tirzepatide is approved and available; retatrutide is not.

**Q: Is it safe to buy retatrutide online or from a med spa?**

A: No product sold as retatrutide outside a Lilly trial is approved or checked by the FDA. Lilly warns these products may contain the wrong amount, the wrong ingredient or contaminants, and the FDA has said compounding pharmacies cannot make it. If you are interested in retatrutide, ask your doctor about clinical trials instead.