Retatrutide

Retatrutide is an investigational synthetic peptide classified as a triple receptor agonist, designed to activate the GIP, GLP-1, and glucagon receptors together rather than one at a time. It contains 39 amino acids and was developed by Eli Lilly under the internal research code LY3437943. It has not been approved by the FDA and is not marketed as a drug for human or animal use.

In short, retatrutide combines three receptor targets in one molecule instead of the single-receptor design used by many other peptides referenced in this article. It remains an unapproved, investigational research compound, not a finished drug product.

All of our reusable peptide pens (V1, V2, V3 and Gansulin) are compared on one page.

Retatrutide is a synthetic peptide studied in laboratory research as a triple agonist acting at GIP, GLP-1, and glucagon receptor sites. It is typically supplied as a lyophilized powder that researchers reconstitute before use. This overview covers hardware and handling only, and nothing here implies human or animal use.

Hardware compatibility notes

• Reusable pens in our catalog accept universal 28G–33G screw-on pen needles.
• Our pens take standard 3 ml (300-unit) glass cartridges with the 11 mm long plunger (stopper), the cartridge we sell. 3 ml cartridges are also made with a shorter, about 8 mm plunger, and a pen is built for one height, so check that a cartridge from another source has the 11 mm long plunger before loading it; the glass looks identical from the outside.

Before loading any cartridge, confirm the stopper length against these specifications. Once reconstituted, store solutions refrigerated and shielded from light, and label vials or cartridges clearly to avoid mix-ups during subsequent laboratory sessions.

What it is

Key point: Retatrutide is an investigational, not-yet-approved triple agonist — a compound designed to activate three receptors at once. It is not FDA approved and is intended for laboratory research use only.

Retatrutide carries the lab code LY3437943. It is a synthetic peptide — a small, lab-built protein-like molecule — made of a chain of 39 linked amino acids, the building blocks that form proteins. It was developed by Eli Lilly.

One molecule, three receptor targets:

• GIP receptor — glucose-dependent insulinotropic polypeptide receptor
• GLP-1 receptor — glucagon-like peptide-1 receptor
• Glucagon receptor — the third target activated by the same molecule

Each receptor is studied for a distinct role in cellular energy and glucose-signaling pathways, which is why researchers classify Retatrutide as a single-molecule, multi-target compound rather than a conventional single-receptor agent. This overview is provided strictly for reference and laboratory research purposes.

Research context and categorization

Retatrutide falls into the metabolic and weight-regulation research category, discussed alongside GLP-1 receptor agonists and dual GIP/GLP-1 receptor agonists. These are compounds studied for their action on incretin-related signaling pathways: GLP-1 agonists target the GLP-1 receptor, while dual agonists such as tirzepatide combine GLP-1 receptor activity with GIP receptor activity in a single molecule. Retatrutide extends that framework by adding a third target, the glucagon receptor, which is why the research literature often labels it a triple receptor agonist.

Investigational Areas

In published trial designs, retatrutide has been studied across several research contexts, described by Eli Lilly as covering:

• Obesity and overweight with a weight-related condition
• Type 2 diabetes
• Knee osteoarthritis
• Obstructive sleep apnea
• Chronic low back pain
• Cardiovascular and kidney outcomes
• Metabolic dysfunction-associated steatotic liver disease

Retatrutide is not approved by the FDA or other regulators, so every listed use remains investigational: still under study, with no confirmed outcomes. Any figures reported in these trials describe research findings only, not established results.

Status

Regulatory status

Retatrutide is research-only and investigational. As of mid-2026, it holds no FDA approval for any use in humans or animals and is not sold as an approved medicine. It remains in Phase 3 clinical trials, the large-scale human studies conducted before a drug can be submitted for regulatory approval. No approval timeline has been confirmed.

Sport status

Retatrutide is prohibited under the WADA Prohibited List, the global anti-doping rulebook. Its primary classification falls under S0 (non-approved substances), which covers compounds lacking established regulatory approval. Some analyses also reference it under peptide hormones and growth factors (S2) or hormone and metabolic modulators (S4). Athletes and competitors subject to WADA testing should treat it as strictly prohibited in all contexts.

Reconstitution notes (general)

Retatrutide is supplied as a lyophilized (freeze-dried) powder. Before lab use, it is mixed with liquid to turn it into a solution. This step is called reconstitution. The concentration of the final solution equals the milligrams of powder in the vial divided by the milliliters of bacteriostatic water added.

Concentration equals the peptide mass in the vial divided by the volume of diluent added. You can use the peptide calculator to work out concentrations easily.

Solution stability is a separate variable from dilution math, and it's worth tracking once a vial is reconstituted:

• Bacteriostatic water carries a small percentage of benzyl alcohol as a preservative. This helps inhibit bacterial growth after a vial is entered, but it does not stop the peptide itself from chemically degrading over time.
• A reconstituted solution is generally less stable than the original lyophilized powder.
• Heat, light, and repeated freeze-thaw cycles all accelerate that degradation.
• Reconstituted vials are typically kept refrigerated and shielded from light, with usable-life estimates taken from the peptide's own reference documentation rather than assumed.

Dilution and handling notes (compound-specific)

Retatrutide ships as a freeze-dried powder, not a ready-to-use liquid, so it must be reconstituted with a diluent before use. Researchers typically pick a water-to-vial ratio that lines up with round numbers on an insulin syringe, which simplifies measuring.

Diluent volume varies with vial size; work out the ratio for a specific vial with a peptide calculator rather than from a fixed reference.

Bacteriostatic water is a common diluent choice because it contains benzyl alcohol as a preservative, which slows bacterial growth and allows repeated draws from the same vial across a refrigerated storage window.

Does benzyl alcohol affect peptide stability?

Benzyl alcohol is well tolerated by many peptides, but it is chemically reactive, and some peptide classes are more sensitive to it than others. This is one reason reconstituted vials are treated as having a limited usable window rather than an indefinite shelf life, and why plain sterile water is sometimes chosen instead for short-term, single-draw use.

Handling best practices

Standard reconstitution handling follows a few consistent steps:

1. Run the diluent slowly down the inner wall of the vial rather than squirting it onto the powder.
2. Roll or swirl the vial gently instead of shaking it. Fast addition or shaking can create foam and may stress the peptide.
3. Be patient with dissolution. Like other long-acting, fatty-acid-modified peptides, retatrutide can take a couple of minutes of gentle rolling to fully clear; a clumped or gel-like appearance at first is normal.

A properly reconstituted vial should be clear and colorless with no visible particles. Cloudiness, a color change, or floating material signal a problem such as clumping, degradation, or a temperature or pH issue — and the vial should be discarded rather than filtered or reheated.

Retatrutide is also light-sensitive in both powder and solution form, so vials should be kept shielded from direct light at all times.

Handling and storage

Proper storage and handling protects material integrity between uses. Follow these guidelines:

• Store reconstituted material in the refrigerator at 2 to 8 degrees Celsius and keep it out of light.
• Wipe the rubber stopper with alcohol before each puncture, and label the vial with the date you mixed it.
• Follow the general roughly 4-week refrigerated window commonly cited for reconstituted peptide solutions. Reports for retatrutide often note about 28 to 30 days when stored properly.
• Discard anything that has turned cloudy or discolored, or that has visible particles floating in it. A color shift, such as a solution fading from a tinted hue to clear, typically signals degradation rather than a vial or cartridge defect.
• Diluents containing a preservative such as benzyl alcohol are generally formulated to extend a solution's usable stability window versus preservative-free diluents; the storage limits above still apply either way.

Frequently asked questions

More in our bacteriostatic water and diluents collection.