# Retatrutide: FDA Status, Research and Uses

> Retatrutide FDA status (not approved), why FDA says it cannot be compounded, phase 2 and phase 3 TRIUMPH trial results, and reported side effects.

- Canonical URL: https://livingpluspeptides.com/peptides/retatrutide/
- Last updated: October 25, 2026
- Publisher: Living+

Retatrutide is an experimental peptide that acts on the GIP, GLP-1 and glucagon receptors. It is not FDA approved, and FDA says it cannot be used in compounding. It has been studied for obesity, type 2 diabetes, knee osteoarthritis pain and sleep apnea in phase 2 and phase 3 trials [1, 6, 7, 8, 9].

## Regulatory status

- FDA approved: No
- 503A compounding: [Not nominated](https://www.fda.gov/media/94155/download). Not listed in any 503A nomination category (list updated May 14, 2026). FDA states retatrutide cannot be used in compounding under federal law and is not a component of an FDA-approved drug (page current Oct 1, 2026).
- 503B bulks list: [Not nominated](https://www.fda.gov/media/94164/download). Not listed in FDA's 503B nomination categories (updated Mar 21, 2025). FDA says it cannot be used in compounding under federal law.
- WADA prohibited: [Unclear](https://www.wada-ama.org/sites/default/files/2025-09/2026list_en_final_clean_september_2025.pdf) (Not named on the 2026 or 2027 List. S0 (non-approved substances) may apply, since it covers substances no government has approved for human use. The 2027 List, in force January 1, 2027, adds peptides as an S0 example.)
- FDA drug shortage: [Not on the shortage list](https://api.fda.gov/drug/shortages.json?search=generic_name:%22retatrutide%22)
- DEA schedule: [Not scheduled](https://www.deadiversion.usdoj.gov/schedules/orangebook/c_cs_alpha.pdf)
- Last verified: November 2, 2026

Checked against: [FDA: Concerns with unapproved GLP-1 drugs used for weight loss](https://www.fda.gov/drugs/drug-alerts-and-statements/fdas-concerns-unapproved-glp-1-drugs-used-weight-loss), [FDA: Bulk drug substances nominated under section 503A (updated May 14, 2026)](https://www.fda.gov/media/94155/download), [FDA: Bulk drug substances nominated under section 503B (updated Mar 21, 2025)](https://www.fda.gov/media/94164/download), [WADA: 2026 Prohibited List](https://www.wada-ama.org/sites/default/files/2025-09/2026list_en_final_clean_september_2025.pdf), [openFDA Drugs@FDA query: retatrutide (no matches)](https://api.fda.gov/drug/drugsfda.json?search=products.active_ingredients.name:%22retatrutide%22), [openFDA drug shortages query: retatrutide](https://api.fda.gov/drug/shortages.json?search=generic_name:%22retatrutide%22), [DEA Diversion: Controlled Substances - Alphabetical Order](https://www.deadiversion.usdoj.gov/schedules/orangebook/c_cs_alpha.pdf)

## Key facts

- Class: Triple agonist of GIP, GLP-1 and glucagon receptors (investigational) [1, 3]
- Amino-acid length: 39 amino acids, built on a GIP backbone, with a fatty side chain [4]
- Half-life: About 6 days (phase 1b study) [2]
- Route used in studies: Under the skin once weekly in studies [1, 6]
- First studied: 2022 (first discovery and human trial reports, as LY3437943) [3, 2]

## How it works

Retatrutide is one peptide built to act on three hormone receptors at once. It binds to the receptors for GIP, GLP-1 and glucagon [1]. GIP and GLP-1 are gut hormones released after eating. Glucagon is a hormone made by the pancreas [3].

In lab tests, retatrutide showed balanced activity at the glucagon and GLP-1 receptors and stronger activity at the GIP receptor [3]. In obese mice, the glucagon part added a rise in energy use on top of the lower food intake driven by the GIP and GLP-1 parts. Together these lowered body weight [3].

The peptide is a chain of 39 amino acids based on the GIP sequence. A fatty acid is attached so that it binds to albumin in the blood, which slows its clearance [4]. A phase 1b study in people with type 2 diabetes found a half-life of about 6 days, which supports once-weekly dosing [2].

Because it is still experimental, these effects come only from research studies. FDA says retatrutide has not been found safe and effective for any condition [9]. In the phase 3 trials, it was tested against placebo, not against approved drugs [6, 7].

## What the research shows

| Study | Year | Participants | Design | Result | Link |
| --- | --- | --- | --- | --- | --- |
| Human trial: TRIUMPH-1 | 2026 | 2,339 adults with obesity, without diabetes (subgroups with knee osteoarthritis or sleep apnea) | Phase 3, randomized, double-blind, placebo-controlled, 80 weeks, 4, 9 or 12 mg weekly | Studied for weight loss: weight fell 17.6% to 25.0% vs 3.9% with placebo. Knee pain scores and apnea events also fell more than with placebo [6] | [Source](https://pubmed.ncbi.nlm.nih.gov/42814954/) |
| Human trial: TRIUMPH-2 | 2026 | 1,152 adults with obesity or overweight and type 2 diabetes | Phase 3, randomized, double-blind, placebo-controlled, 80 weeks, 4, 9 or 12 mg weekly | Weight fell 11.9% to 18.8% vs 5.1% with placebo [7] | [Source](https://pubmed.ncbi.nlm.nih.gov/42810372/) |
| Human trial: TRIUMPH-1-OSA and TRIUMPH-2-OSA | 2026 | 691 adults with moderate to severe sleep apnea (243 and 448) | Two phase 3, randomized, double-blind, placebo-controlled trials, 80 weeks | Studied for sleep apnea: apnea-hypopnea index fell more than with placebo at 9 and 12 mg [8] | [Source](https://pubmed.ncbi.nlm.nih.gov/42904878/) |
| Human trial: Phase 2 obesity trial | 2023 | 338 adults with obesity or overweight | Phase 2, randomized, double-blind, placebo-controlled, 48 weeks, 1 to 12 mg weekly | Weight fell 8.7% to 24.2% at 48 weeks vs 2.1% with placebo [1] | [Source](https://pubmed.ncbi.nlm.nih.gov/37366315/) |
| Human trial: Phase 2 type 2 diabetes trial | 2023 | 281 adults with type 2 diabetes | Phase 2, randomized, double-blind, placebo and dulaglutide controlled, 36 weeks | A1c fell up to 2.02 points at 24 weeks vs 0.01 with placebo [5] | [Source](https://pubmed.ncbi.nlm.nih.gov/37385280/) |
| Human trial: Phase 1b (LY3437943) | 2022 | 72 adults with type 2 diabetes | Phase 1b, randomized, double-blind, placebo-controlled, multiple ascending dose, 12 weeks | Half-life about 6 days; stomach side effects were the most common [2] | [Source](https://pubmed.ncbi.nlm.nih.gov/36354040/) |
| Animal study: Discovery study (LY3437943) | 2022 | Cell lines, obese mice, and a single-dose phase 1 study | Lab, animal and phase 1 single ascending dose study | Acted on all three receptors and lowered body weight in obese mice [3] | [Source](https://pubmed.ncbi.nlm.nih.gov/35985340/) |

## Doses used in studies

The phase 3 TRIUMPH trials gave 4 mg, 9 mg or 12 mg once weekly for 80 weeks [6, 7]. The phase 2 obesity trial tested 1 mg to 12 mg once weekly for 48 weeks, with some groups starting at 2 mg or 4 mg and stepping up [1].

The phase 1b study tested weekly doses from 0.5 mg up to a stepped schedule ending at 12 mg [2]. There is no FDA-approved dose, because retatrutide is not an approved drug [9].

**Dosing is set by a licensed provider.**

## Side effects and safety

In trials, stomach side effects were the most common. In the phase 2 obesity trial they were dose-related, mostly mild to moderate, and less common with a lower starting dose. Heart rate rose with dose, peaked at 24 weeks and then declined [1].

In TRIUMPH-2, diarrhea occurred in 27% to 34% of retatrutide groups vs 13% on placebo, and nausea in 14% to 28% vs 8%. Low blood pressure and dysesthesia (abnormal skin sensations) were more frequent than with placebo. Stopping for side effects or death was 12% with 9 mg and 8% with 12 mg, vs 5% with placebo [7].

FDA warns that products sold as retatrutide are unapproved drugs. FDA says retatrutide cannot be used in compounding under federal law, is not a component of any FDA-approved drug, and has not been found safe and effective for any condition [9].

- [FDA: Concerns with unapproved GLP-1 drugs used for weight loss, including retatrutide (page current as of Oct 1, 2026)](https://www.fda.gov/drugs/drug-alerts-and-statements/fdas-concerns-unapproved-glp-1-drugs-used-weight-loss) (2026-10-01)

## Legal and regulatory status

- 2026-10-01: FDA's GLP-1 concerns page states that retatrutide cannot be used in compounding under federal law and is not a component of any FDA-approved drug. It lists warning letters to companies marketing unapproved drugs such as retatrutide [9]. [Source](https://www.fda.gov/drugs/drug-alerts-and-statements/fdas-concerns-unapproved-glp-1-drugs-used-weight-loss)
- 2026-05-14: Retatrutide does not appear in any category of FDA's list of bulk substances nominated for 503A compounding (list updated May 14, 2026) [10]. [Source](https://www.fda.gov/media/94155/download)
- 2026-01-01: The WADA 2026 Prohibited List took effect. Its S0 class bans drugs in clinical development with no approval for human use. WADA does not name retatrutide, so its status rests on that general wording [12]. [Source](https://www.wada-ama.org/sites/default/files/2025-09/2026list_en_final_clean_september_2025.pdf)

See every peptide's status side by side in the [Peptide Status Tracker](https://livingpluspeptides.com/regulation/tracker/#row-retatrutide).

## Frequently asked questions

### Is retatrutide FDA approved?

No. FDA says retatrutide is not a component of any FDA-approved drug and has not been found safe and effective for any condition [9].

### Can retatrutide be compounded?

No. FDA says retatrutide cannot be used in compounding under federal law [9]. It does not appear on FDA's 503A or 503B nomination category lists [10, 11].

### Is it legal to sell retatrutide online?

FDA calls retatrutide an unapproved drug and has sent warning letters to companies marketing it [9].

### How much weight loss was seen in retatrutide trials?

In the phase 3 TRIUMPH-1 trial, weight fell 17.6% to 25.0% over 80 weeks, vs 3.9% with placebo [6].

### What is the difference between retatrutide and tirzepatide?

Tirzepatide acts on GIP and GLP-1 receptors. Retatrutide also acts on the glucagon receptor [1].

### What side effects were reported with retatrutide?

Stomach side effects such as diarrhea and nausea were most common. Low blood pressure, skin sensation changes and a higher heart rate were also reported [1, 7].

### Is retatrutide banned in sports?

Unclear. WADA's S0 class bans substances with no approval for human use. WADA does not name retatrutide, so this status is not explicit [12].

### How long does retatrutide last in the body?

A phase 1b study found a half-life of about 6 days [2].

## Sources

1. [Jastreboff et al. 2023, NEJM: Retatrutide phase 2 obesity trial (PubMed)](https://pubmed.ncbi.nlm.nih.gov/37366315/)
2. [Urva et al. 2022, Lancet: LY3437943 phase 1b in type 2 diabetes (PubMed)](https://pubmed.ncbi.nlm.nih.gov/36354040/)
3. [Coskun et al. 2022, Cell Metab: LY3437943 from discovery to clinical proof of concept (PubMed)](https://pubmed.ncbi.nlm.nih.gov/35985340/)
4. [Rapid Commun Mass Spectrom 2026: Detection of retatrutide by LC-HRMS (PMC)](https://pmc.ncbi.nlm.nih.gov/articles/PMC13578828/)
5. [Rosenstock et al. 2023, Lancet: Retatrutide phase 2 in type 2 diabetes (PubMed)](https://pubmed.ncbi.nlm.nih.gov/37385280/)
6. [Jastreboff et al. 2026, NEJM: TRIUMPH-1 (PubMed)](https://pubmed.ncbi.nlm.nih.gov/42814954/)
7. [Bellido et al. 2026, Lancet: TRIUMPH-2 (PubMed)](https://pubmed.ncbi.nlm.nih.gov/42810372/)
8. [Grunstein et al. 2026, NEJM: Retatrutide for obstructive sleep apnea (PubMed)](https://pubmed.ncbi.nlm.nih.gov/42904878/)
9. [FDA: Concerns with unapproved GLP-1 drugs used for weight loss](https://www.fda.gov/drugs/drug-alerts-and-statements/fdas-concerns-unapproved-glp-1-drugs-used-weight-loss)
10. [FDA: Bulk drug substances nominated for use in compounding under section 503A (updated May 14, 2026)](https://www.fda.gov/media/94155/download)
11. [FDA: Bulk drug substances nominated for use in compounding under section 503B (updated Mar 21, 2025)](https://www.fda.gov/media/94164/download)
12. [WADA: 2026 Prohibited List](https://www.wada-ama.org/sites/default/files/2025-09/2026list_en_final_clean_september_2025.pdf)

Educational information, not medical advice. This site sells nothing.