Retatrutide Calculator
Also known as: LY3437943
What is Retatrutide?
Retatrutide is an investigational triple agonist of GIP, GLP-1, and glucagon receptors developed by Eli Lilly. In Phase 2 obesity trials, retatrutide produced approximately 24% mean body-weight reduction at 48 weeks at the 12 mg dose — the largest weight-loss effect reported for any GLP-1-class compound to date. It is not yet FDA-approved; access is via clinical trial enrolment or regulated compounding. Trial protocols use a stepwise titration starting at 2 mg weekly. At a 10 mg vial reconstituted with 2 mL of BAC water, a 2 mg dose draws to 40 units on a U-100 insulin syringe.
| 4 mg | lyophilized powder |
| 8 mg | lyophilized powder |
| 10 mg | lyophilized powder |
| 12 mg | lyophilized powder |
| 16 mg | lyophilized powder |
| 2 mg | ≈ 40 U-100 units (at 10mg / 2mL) |
| 4 mg | ≈ 80 U-100 units (at 10mg / 2mL) |
| 6 mg | ≈ 120 U-100 units (at 10mg / 2mL) |
| 8 mg | ≈ 160 U-100 units (at 10mg / 2mL) |
| 12 mg | ≈ 240 U-100 units (at 10mg / 2mL) |
How it's typically prepared
Reconstitute slowly with BAC water against the inner wall, swirl, refrigerate. Storage stability data for compounded retatrutide is limited — follow your compounding pharmacy's specific guidance.
Retatrutide Side Effects
The Phase 2 retatrutide trial (Jastreboff et al., NEJM 2023) reported gastrointestinal adverse events as the dominant side-effect pattern, consistent with other GLP-1-class drugs. The investigational status of retatrutide and the limited population size of pre-Phase-3 trials mean less is known about long-term and rare adverse events than for FDA-approved tirzepatide or semaglutide. The list below summarises events reported in published trial data — it is not a complete safety profile.
- Nausea
- Vomiting
- Diarrhea
- Constipation
- Decreased appetite
- Injection-site reactions
- Gallbladder events (cholelithiasis, cholecystitis) — reported in some Phase 2 participants
- Increased heart rate
- Possible pancreatitis (per GLP-1 class data — not specifically reported in retatrutide trials)
Frequently asked questions
- Is retatrutide FDA-approved?
- As of April 2026, retatrutide is investigational. It is being evaluated in Phase 3 trials for obesity and type 2 diabetes.
- How does retatrutide compare to tirzepatide?
- In Phase 2 trials, retatrutide produced approximately 24% mean weight loss at 48 weeks at 12 mg, compared with about 22.5% for tirzepatide at 15 mg in the SURMOUNT-1 trial — though direct head-to-head data is not yet available.
- What's a typical starting dose?
- Trial protocols typically start at 2 mg once weekly with monthly titration up to 12 mg.
Where researchers source this
Vendors below have been manually vetted for third-party COA practice and shipping reliability. Verify the current Certificate of Analysis on the vendor's product page before purchase.
Apollo Peptide SciencesUSA-based research vendor with third-party HPLC and mass spectrometry COAs plus endotoxin reports published per product. Specialty in GLP-1 reference compounds (Semaglutide, Tirzepatide, Retatrutide). Ships within 48 hours via USPS Priority/Express. 120-day cookie window — the longest US attribution in the space.
Buy Retatrutide (GLP-3 R 30mg) →Affiliate link — we may earn a commission at no extra cost to you.
EU-based vendor (Slovakia, since 2015) shipping to EU, UK, and Switzerland. The only European supplier publishing all seven test parameters per batch (purity, identity, content, bioburden, endotoxins, heavy metals class 1 & 2). Manufacturer is cGMP / ISO 9001 / ISO 13485 compliant.
Buy GLP-3 10mg (Retatrutide) →Affiliate link — we may earn a commission at no extra cost to you.
Other GLP-1 peptides
PeptideDose is an educational reference. It is not medical advice and does not replace consultation with a licensed healthcare provider. Doses shown in presets are derived from published protocols and product labels — they are not personal recommendations.