Retatrutide

Fat LossInvestigational triple agonistEmerging

Also known as: LY3437943, Triple GIP/GLP-1/glucagon agonist

Retatrutide (also called LY3437943 or Triple GIP/GLP-1/glucagon agonist) is an investigational triple agonist in the GLP-1 Agonist class. Retatrutide is a single peptide agonist at three receptors — GIP, GLP-1 and glucagon — with an acyl chain supporting weekly dosing.

Calculate Dose

For research use only.

Key Facts

CAS: 2381089-83-2
Molecular Weight (MW): ~4731 g/mol
Half-life: ~6 days (weekly injection in trials)
FDA status: Investigational New Drug (IND)
Evidence level: Clinical Trial Evidence
Human dose established: Yes
Administration Route: Subcutaneous
Frequency: Once weekly
Last updated: Sep 26, 2026
Reviewed: Aug 30, 2026
Targets: GIP receptorGLP-1 receptorGlucagon receptor

Vendor price snapshot

Each vendor counts once, at the median price per mg of its own listings; the typical range is the middle half of vendors. From public vendor listings collected between Nov 2025 and Sep 2026, so confirm the live price on the vendor site. Peptide Library does not sell peptides.

Vendors listing this peptide: 32
Listed offers: 133
Median price per mg: $9.87/mg; Typical $6.61–$14.15/mg

Open calculator · Compare vendors

Research summary

Peptide Library's Retatrutide profile summarises 5 cited studies listed in the Science section, the compound's regulatory status, and research-protocol parameters reported for it. It is a research reference, not medical advice.

Retatrutide dosage chart

Retatrutide has no FDA-approved dosage. Human dosing comes from Eli Lilly's registered trial programme, where doses of 1–12 mg subcutaneously once weekly were studied in phase 2 with published results, reached by stepwise titration inside a monitored protocol. The first phase 3 trial to publish, TRANSCEND-T2D-1 (2026), gave 4, 9 or 12 mg once weekly for 40 weeks in type 2 diabetes; the obesity trials (TRIUMPH) have not yet published results, so there is no established maintenance dose outside a trial.

Clinical Trial Evidence

Dosage evidence summary for Retatrutide
Human dosing established	Yes
Studied dose range	1–12 mg once weekly in phase 2 and 3 trials
Route	Subcutaneous
Frequency	Once weekly
Duration studied	36–48 weeks in the published phase 2 trials; 40 weeks in the first published phase 3 trial
Titration	Stepwise escalation inside the trial protocol, typically starting at 2 mg and increasing every 4 weeks. The published dose range is the range studied, not a schedule for use.
Evidence level	Clinical Trial Evidence
Last reviewed	2026-09-05

Research-reported dosing

Doses as studied, one row per regimen. Different trials used different regimens; they are listed separately rather than averaged.

Research-reported dosing for Retatrutide, one row per studied regimen
Study / context	Population	Dose	Route	Frequency	Duration	Outcome studied	Source
Phase 2 obesity trial (Jastreboff et al., 2023)Clinical trial · Phase 2 double-blind randomised placebo-controlled trial	Adults with obesity, or overweight with a weight-related condition (n=338)	1 mg, 4 mg, 8 mg or 12 mg	Subcutaneous	Once weekly	48 weeks	Percentage change in body weight	Jastreboff AM et al. Triple-Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial. N Engl J Med. 2023.
Phase 2 type 2 diabetes trial (Rosenstock et al., 2023)Clinical trial · Phase 2 double-blind randomised controlled trial	Adults with type 2 diabetes (n=281)	0.5 mg, 4 mg, 8 mg or 12 mg	Subcutaneous	Once weekly	36 weeks	Change in glycated haemoglobin	Rosenstock J et al. Retatrutide, a GIP, GLP-1 and glucagon receptor agonist, for people with type 2 diabetes: a randomised, double-blind, placebo- and active-controlled, parallel-group, phase 2 trial. Lancet. 2023.
Phase 2 MASLD substudy (Sanyal et al., 2024)Clinical trial · Phase 2 substudy	Adults with obesity and metabolic dysfunction-associated steatotic liver disease	1 mg, 4 mg, 8 mg or 12 mg	Subcutaneous	Once weekly	48 weeks	Liver fat content	Sanyal AJ et al. Triple hormone receptor agonist retatrutide for metabolic dysfunction-associated steatotic liver disease. Nat Med. 2024.
Phase 3 type 2 diabetes monotherapy trial (TRANSCEND-T2D-1; NCT06354660)Clinical trial · Phase 3 double-blind randomised placebo-controlled trial	Adults with type 2 diabetes inadequately controlled by diet and exercise (n=537)	4 mg, 9 mg or 12 mg	Subcutaneous	Once weekly	40 weeks	Change in glycated haemoglobin; body weight a key secondary endpoint	Bajaj HS et al. Efficacy and safety of retatrutide, a GIP, GLP-1, and glucagon receptor agonist, in people with type 2 diabetes and inadequate glycaemic control with diet and exercise (TRANSCEND-T2D-1): a double-blind, randomised, phase 3 trial. Lancet. 2026.
NCT06260722 — phase 3 versus semaglutide, no results yetClinical trial · Phase 3, active not recruiting, no results posted	Adults with obesity (n=1250)	Per trial protocol; not yet published	Subcutaneous	Once weekly	Per trial protocol	Body weight versus semaglutide	NCT06260722 — Effect of Retatrutide Compared With Semaglutide in Adult Participants With Obesity

Where sources disagree

Retatrutide is not an FDA-approved product. Several DailyMed listings appear under its name, but they are submitted by a cross-border e-commerce labeller rather than representing an FDA-approved prescribing information document. A DailyMed listing is not evidence of approval.
The 12 mg weekly figure is the highest dose studied in phase 2, reached by protocol-driven titration under trial monitoring. It is not a target dose, and dose-dependent gastrointestinal adverse effects were reported across the escalation range.

Reconstitution

Common research vial sizes: 10 mg, 20 mg, 30 mg.

Reconstitution arithmetic for Retatrutide
Vial	Bacteriostatic water	Concentration	Per 0.01 mL
10 mg	2 mL	5 mg/mL	50 mcg per 0.01 mL
30 mg	3 mL	10 mg/mL	100 mcg per 0.01 mL

These figures are arithmetic only — they convert a vial and a volume into a concentration. They are not a recommendation to take any dose.

Calculate reconstitution & dose →

Handling & administration

Reconstitution Guide: Varies
Injection Sites: AbdomenThigh
Concentration Example: N/A
Timing Notes: Clinical-trial context only; not an approved label
Expected Onset: 1-4 weeks

How to reconstitute Retatrutide

Check the vial size and diluent volume. The profile example for Retatrutide is: Varies.
Swab both vial stoppers and draw the bacteriostatic water into a sterile syringe.
Add the water slowly down the inside wall of the peptide vial so it does not jet onto the powder, then swirl gently until the solution is clear. Do not shake.
Record the resulting concentration: N/A.
Label the vial with the date and concentration, refrigerate it (see Storage & stability below), and use the calculator preset to convert a dose in mcg into syringe units.

Open the peptide calculator with the Retatrutide preset →

Sequence & molecular data

Sequence and molecular data for Retatrutide
Amino acid sequence	Not publicly disclosed (triple agonist)
Molecular formula	C221H342N46O68
Molecular weight	~4731 g/mol
CAS number	2381089-83-2
Half-life	~6 days (weekly injection in trials)
Appearance	White lyophilized powder
Formulation	Lyophilized Powder

Identifiers link to the public PubChem, FDA Substance Registration (UNII), ChEMBL and DrugBank records for the same entity.

Science

Mechanism of Action

Retatrutide is a single peptide agonist at three receptors — GIP, GLP-1 and glucagon — with an acyl chain supporting weekly dosing. Each arm contributes something different. GLP-1 receptor activation drives glucose-dependent insulin secretion and central appetite suppression; GIP receptor activation adds effects on adipose metabolism and hindbrain signalling; glucagon receptor activation raises hepatic energy expenditure and promotes fat oxidation, a catabolic effect that opposes the weight-sparing tendency of incretin action alone. Balancing glucagon agonism against its hyperglycaemic potential is the central design problem of the class, resolved here by pairing it with sufficient incretin activity.

Origin

Synthetic fatty-acylated triple agonist (Lilly).

Targets

GIP receptorGLP-1 receptorGlucagon receptor

Studies

Regulatory & research status

Retatrutide has been studied under an Investigational New Drug application. It is not approved for marketing.

Regulatory and research status for Retatrutide
FDA status	Investigational New Drug (IND)
Availability	Research-Only
WADA (sport)	Banned in Sport
Library classification	Clinical Trial

Benefits

Investigational obesity/T2D candidateTriple-incretin pharmacology

Retatrutide side effects

The effects below are those reported in Retatrutide clinical trials; long-term safety data may still be limited.

Side Effects

Nausea
Diarrhea
Constipation
Increased heart rate

Contraindications

Thyroid cancer history

Stacking

Common stacking partners

Diet/exercise

Combinations that include Retatrutide, with the proposed rationale, an evidence grade and what is not established, are catalogued in the peptide stacks directory.

Storage & stability

Lyophilized (freeze-dried) peptide powder is far more stable than the reconstituted solution. Keep sealed vials cold, dry and away from light; long-term storage is typically frozen, with short-term refrigeration for vials in use.

Once reconstituted in bacteriostatic water, keep the solution refrigerated, avoid repeated freeze–thaw cycles and agitation, and label the vial with the reconstitution date and concentration. Discard any solution that turns cloudy or shows particulates.

Degradation rates differ by sequence: peptides containing methionine, cysteine, asparagine or glutamine are more prone to oxidation and deamidation, so shelf life after reconstitution is compound-specific rather than universal.

Read the full guide: how to store peptides before and after reconstitution →

Source: Manning MC, Chou DK, Murphy BM, Payne RW, Katayama DS. Stability of protein pharmaceuticals: an update. Pharm Res. 2010;27(4):544–575. (PMID 20143256). General guidance for research handling; not product-specific instructions.

Retatrutide: frequently asked questions

What is Retatrutide?

Lilly triple agonist (GIP, GLP-1, glucagon receptors). The first published phase 3 trial, TRANSCEND-T2D-1 (Lancet, 2026), lowered HbA1c and body weight over 40 weeks in type 2 diabetes; the TRIUMPH obesity trials have not yet published peer-reviewed results. Not FDA-approved. Retatrutide is a single peptide agonist at three receptors — GIP, GLP-1 and glucagon — with an acyl chain supporting weekly dosing. Each arm contributes something different. GLP-1 receptor activation drives glucose-dependent insulin secretion and central appetite suppression; GIP receptor activation adds effects on adipose metabolism and hindbrain signalling; glucagon receptor activation raises hepatic energy expenditure and promotes fat oxidation, a catabolic effect that opposes the weight-sparing tendency of incretin action alone.

What are the side effects of Retatrutide?

Side effects recorded for Retatrutide from clinical-trial reports include nausea, diarrhea, constipation and increased heart rate. Cautions recorded on this profile: thyroid cancer history. It is on the WADA Prohibited List for athletes. This is reference information, not medical advice.

How does Retatrutide work?

Retatrutide is a single peptide agonist at three receptors — GIP, GLP-1 and glucagon — with an acyl chain supporting weekly dosing. Each arm contributes something different.

Is Retatrutide FDA approved?

No. Retatrutide is investigational: it is in clinical development and has not been approved by the FDA for any indication. Investigational status means trials are ongoing or complete but regulatory review has not resulted in approval, and efficacy and safety are still being established.

What is the half-life of Retatrutide?

Reported half-life for Retatrutide is ~6 days (weekly injection in trials). Half-life describes how long the compound persists in circulation, not how long any effect lasts, and published figures vary with route of administration, formulation and the population studied.

What is the amino acid sequence of Retatrutide?

Retatrutide has the sequence Not publicly disclosed (triple agonist). Its molecular formula is C221H342N46O68.

Is Retatrutide banned in sport?

Retatrutide is recorded here as prohibited in sport. Athletes subject to anti-doping rules should check the current WADA Prohibited List directly, since it is revised annually and classifications change.

How long does Retatrutide take to show effects in research protocols?

The research protocol on this profile lists an expected onset of 1-4 weeks. This is a protocol note describing when studies and researchers report observing changes, not a measured clinical outcome, and it varies with the model, dose and endpoint studied.

Where is Retatrutide administered in research protocols?

Research protocols on this profile use subcutaneous administration, with recorded sites including abdomen, thigh. Site rotation and sterile technique are standard practice in the research literature; this describes protocol conditions and is not guidance for use.

References

Related research, comparisons & guides

Related peptides

Compiled by Peptide Library Editorial · Reviewed Aug 30, 2026 · Updated Sep 26, 2026 · Version 6

This Retatrutide profile is compiled from published literature (5 cited studies linked above), public regulatory records and chemical registries. It describes what research reports; it is not medical advice, and nothing here is a dosing recommendation for humans. Peptide Library does not sell peptides. Editorial policy · How profiles are compiled · Report an error

Track Retatrutide research, inventory and reconstitution in the free Peptide Library app. Get the app for iOS or Android →