Retatrutide Research Guide: Triple Agonist Structure, COA and Handling
Retatrutide is a 39-amino-acid synthetic peptide that activates three receptors: GIP, GLP-1 and glucagon. Labs use it in receptor-signaling research as the reference triple agonist, and alongside semaglutide and tirzepatide to compare one-, two- and three-receptor compounds. This page covers its structure, what a retatrutide certificate of analysis should show, and how to handle the lyophilized powder, using FRO Peptides’ own published lot reports as the example.
Retatrutide at a glance
| Class | GIP / GLP-1 / glucagon receptor triple agonist (research compound) |
|---|---|
| Length | 39 amino acids, C-terminal amide |
| Molecular formula | C221H342N46O68 |
| Molecular weight | ≈ 4,731.3 g/mol |
| CAS number | 2381089-83-2 |
| Key modifications | Several non-natural amino acids, including Aib, for enzyme resistance; a C20 fatty diacid side chain on a lysine for albumin binding |
| Supplied as | Lyophilized white powder in sealed vials |
| FRO vial sizes | 10mg, 15mg, 20mg, 30mg |
| FRO tested purity | 99.9% (10mg, MWPT-UJJ4) and 99.52% (30mg, FP9B-P754), HPLC |
How the molecule is built
Like tirzepatide, retatrutide’s backbone starts from the GIP sequence and is engineered so one chain binds more than one receptor. Retatrutide goes a step further and adds glucagon-receptor activity. Non-natural amino acids protect it from enzymatic cleavage, and a 20-carbon fatty diacid side chain binds albumin, which keeps the molecule intact far longer in biological matrices than an unmodified peptide.
For lab work, the side chain is part of the molecule’s identity, so a sample missing it, or carrying a damaged one, is not retatrutide even if the backbone is intact. The lipid portion also makes it more sensitive to aggressive mixing and repeated freeze-thaw than a plain peptide.
Why labs use it
- Three-receptor signaling. It is used to study how GIP, GLP-1 and glucagon receptor signaling interact when all three are triggered by one molecule.
- Glucagon receptor research. Glucagon-receptor activity is the piece that separates it from dual agonists, so it is used to isolate what that third receptor adds in cell and tissue models.
- Comparator sets. With semaglutide (one receptor) and tirzepatide (two), it completes a standard comparison set for receptor-selectivity studies.
How to read a retatrutide certificate of analysis
A COA is only useful if you know what each line proves. FRO has two retatrutide reports on file from AccuMark Labs, both published 09/07/2026:
| Test | 10mg (MWPT-UJJ4) | 30mg (FP9B-P754) | What it tells you |
|---|---|---|---|
| Identity | Retatrutide, conforms | Retatrutide, conforms | The main compound in the vial matches retatrutide. |
| HPLC purity | 99.9% | 99.52% | Share of the sample that is the target peptide, measured by UV at 220 nm, against a spec of more than 98.0%. Both chromatograms show one sharp main peak at about 6.4 to 6.6 minutes. |
| Quantity | 10.37 mg in a 10 mg vial | 30.97 mg in a 30 mg vial | How much peptide is actually in the vial. Both lots came in slightly above the label. Many COAs skip this line, but it is the one that catches underfilled vials. |
| Endotoxin (LAL) | Pass, ≤ 5.0 EU/mL | Not tested | Bacterial endotoxin is below the limit. |
| Sterility screen (PCR) | Not detected, pass | Not tested | No microbial DNA detected in the sample. |
Both full reports, chromatograms included, are free to open in the Retatrutide COA library. Match the code on your vial to the right report.
HPLC purity vs. structural confirmation
HPLC purity tells you how clean the sample is. It does not, on its own, prove every part of the structure is intact. For a lipidated peptide like retatrutide, mass spectrometry is the method that confirms the full molecular weight, including the fatty acid side chain. FRO’s current retatrutide reports cover identity, HPLC purity and measured quantity, plus endotoxin and sterility on the 10mg lot. FRO has additional testing underway at Vanguard Laboratory, an ISO 17025 lab, and new results are added to the COA library as they come in.
Red flags on any supplier’s COA
- No lot or sample code, or a code that doesn’t match the vial.
- No lab name, or a lab you can’t find.
- Purity with no chromatogram.
- No measured quantity, only the label claim.
- One report covering every vial size, when the sizes are filled from different lots.
- The same report reused across several products or years.
Storage and handling for research use
- Lyophilized powder: store frozen (−20 °C), sealed and protected from light. Let the vial reach room temperature before opening to avoid condensation.
- Reconstitution: add bacteriostatic water slowly down the vial wall and swirl gently. Don’t shake, because agitation can damage the lipidated side chain. Use the peptide reconstitution calculator to work out concentration for your protocol.
- After reconstitution: refrigerate at 2–8 °C, protect from light, and use within your protocol’s defined window.
- Avoid repeated freeze-thaw. If you need to store reconstituted material frozen, split it into single-use aliquots first.
Frequently asked questions
Does FRO Peptides publish a COA for retatrutide?
Yes. Reports for the 10mg and 30mg lots from AccuMark Labs, an independent lab, are in the COA library, chromatograms included.
What purity is FRO’s retatrutide?
The current lots tested at 99.9% (10mg) and 99.52% (30mg) by HPLC, against a specification of more than 98.0%. The 10mg lot also passed endotoxin and PCR sterility screening.
How is retatrutide different from tirzepatide?
Tirzepatide activates two receptors (GIP and GLP-1). Retatrutide adds a third, the glucagon receptor. See the tirzepatide research guide for the dual agonist.
What is the difference between the vial sizes?
Only the quantity of peptide. The 10mg, 15mg, 20mg and 30mg vials contain the same compound.
Is retatrutide from FRO for human use?
No. FRO sells retatrutide strictly for laboratory and analytical research. It is not for human or veterinary use.
View Retatrutide research peptide (10mg–30mg) →
Lot reports published in the COA library. Ships next business day, FedEx 2-Day.
For laboratory research use only. Not for human or veterinary use. Not a drug, food, or cosmetic under FDA regulations. Nothing on this page is medical advice.