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Specimen Atlas of Research Peptides30 plates · MIT
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XIXPlate XIXReviewed 2026-04-25

Retatrutide

GLP-1 / GIP / Glucagon Triple Agonist

also known as LY3437943

Investigational triple-receptor agonist of GLP-1, GIP, and glucagon receptors developed by Eli Lilly. The Phase 2 trial (Jastreboff et al., NEJM 2023) demonstrated 24.2% body-weight reduction at 12 mg over 48 weeks — the largest weight-loss effect of any peptide tested in obesity. Phase 3 trials ongoing as of 2026.

§ I

At a glance

Weekly dose
1–12 mg
[jastreboff-2023-reta]
Body-weight ↓
24.2%
[jastreboff-2023-reta]
Half-life (est)
~6 days
Route

SQ · Abdomen · Once weekly

§ II

Mechanism

Primary target — GLP-1R + GIPR + Glucagon receptor (triple agonism) [jastreboff-2023-reta].

Pathway — Triple-receptor activation → ↑insulin (GLP-1+GIP), ↓gastric emptying, ↑lipid handling, ↑energy expenditure (glucagon component) [jastreboff-2023-reta].

Downstream effect — Maximal weight loss across class. Glucagon component drives lipolysis and energy expenditure beyond GLP-1+GIP alone [jastreboff-2023-reta].

Origin — Synthetic peptide engineered for balanced affinity at three incretin / glucagon receptors [jastreboff-2023-reta].

§ III

Dosage

Protocols described in the cited literature; not medical advice.

ParameterValue
Standard dose12 mg / week (max efficacy) [jastreboff-2023-reta]Phase 2 trial dose. Phase 3 dosing TBD.
FrequencyOnce weekly
Titration schedule2 mg → 4 mg → 8 mg → 12 mg over 16 weeks
Evidence basisPhase 2 trial; Phase 3 ongoing [jastreboff-2023-reta]
DurationIndefinite for chronic indication (presumed)
ReconstitutionInvestigational; not commercially available
TimingAny time of day
Half-life~6 days (estimated from class)
§ III · b

Reconstitution

A pure mass-to-volume utility. Enter what you have in the vial; the atlas computes the volume per dose. No prescription information.

Inputs
The calculator does pure mass-to-volume math. It does not recommend a dose. Refer to Retatrutide's cited literature for protocol specifics.
Volumetric outputFig. C — reconstitution math
Volume per dose
0.042mL
≈ 4.2 units on a U-100 insulin syringe
Concentration
6000
mcg per mL
Doses per vial
48
at this dose
§ V

Adverse events

Severities follow the FDA / CTCAE convention.

GI symptomsmoderate
Nausea, vomiting, diarrhea (very common, dose-dependent) [jastreboff-2023-reta]
Heart ratemoderate
↑ resting HR (3–7 bpm at 12 mg) [jastreboff-2023-reta]
Glucose handlingmoderate
Glycemic improvement; rare hyperglycemia from glucagon component
Pancreatitis risksevere
Class warning
Thyroid C-cell tumourssevere
Class warning (presumed)
Pregnancy / OBsevere
Avoid (insufficient data)
Absolute contraindications
  • — MTC personal or family history (presumed class effect)
  • — Pregnancy / breastfeeding
Relative contraindications
  • — Severe gastroparesis
  • — History of pancreatitis
  • — Severe cardiovascular disease (HR signal)
§ VI

Administration

  1. 01
    Reconstitution

    Investigational peptide. Research vials reconstituted with bacteriostatic water per label.

  2. 02
    Injection site

    SQ — abdomen, thigh, or upper arm. Rotate weekly.

  3. 03
    Timing

    Once weekly, same day.

  4. 04
    Storage

    Refrigerate 2–8 °C. Light-protected.

  5. 05
    Needle

    27–31G, 4–8 mm insulin syringe.

Appendix

Sources

24%

of 41 rendered claims carry a resolvable citation.

  1. [jastreboff-2023-reta]
    Jastreboff 2023 — Triple-Hormone-Receptor Agonist Retatrutide for Obesity
    N Engl J Med, 2023
    PubMed →
Plate composed 2026-04-25 · maturity reviewed · schema v1 · Contributors: peptidesdb-core · 31 fields uncited — open contributions
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