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Retatrutide

GLP-1 / GIP / Glucagon Triple Agonist

Also known as: LY3437943

An investigational triple agonist of GLP-1, GIP, & glucagon receptors showing 24% mean weight loss in Phase II — the highest in any clinical peptide trial to date.

Typical Dose

4–12 mg once weekly (investigational)

Route

Subcutaneous injection (once weekly)

Cycle

Continuous (Phase III protocols: 48–72 weeks)

Half-life

~6 days (estimated)

Storage

Reconstituted: 2–8°C, use within 28 days.

Overview

Retatrutide adds glucagon receptor agonism to the dual GLP-1/GIP mechanism of tirzepatide. Glucagon receptor activation increases hepatic glucose output & thermogenesis — a mechanism that complements GLP-1's appetite suppression & GIP's adipose tissue effects. The net result in Phase II trials was 24.2% mean body weight reduction at 12 mg over 48 weeks, the highest figure reported for any pharmacotherapy.

As of 2026, retatrutide is in Phase III trials. Compounded versions have begun to circulate. Quality verification is important given the early stage of manufacturing experience.

Quick Start Guide

1

Currently only available through clinical trials or compounding pharmacies.

2

Typical starting dose: 2 mg once weekly, escalating to target dose over 24 weeks.

3

Same injection technique as semaglutide/tirzepatide: SubQ abdomen/thigh.

Research Indications

Obesity / weight loss

Most Effective

Phase II: 24.2% mean weight loss at 12 mg, 48 weeks. Phase III ongoing.

Type 2 diabetes

Effective

Significant HbA1c reduction observed in Phase II.

Non-alcoholic fatty liver disease

Research Only

Glucagon agonism drives hepatic lipid clearance; liver fat reduction expected but not a primary endpoint yet.

Research Protocols

Weight loss (investigational escalation)

Escalate every 4–8 weeks per Phase II protocol

Dose

2 → 4 → 8 → 12 mg

Frequency

Once weekly SubQ

Route

SubQ abdomen/thigh

Peptide Interactions

Do not combine; same receptor class.

Do not combine.

Side Effects & Safety

Common

  • Nausea
  • Vomiting
  • Diarrhea
  • Decreased appetite

Uncommon

  • Tachycardia (glucagon effect)
  • Hypoglycemia with insulin co-use
  • Pancreatitis (rare)

When to Stop

  • History of MEN2 or medullary thyroid carcinoma
  • Suspected pancreatitis
  • Signs of allergic reaction

How to Reconstitute

1

Wipe stopper with alcohol.

2

Inject bacteriostatic water down inner vial wall slowly.

3

Swirl gently until dissolved.

4

Label & refrigerate at 2–8°C.

Dosing math: No standardized compounded concentration yet. Confirm with supplier. Typically 2–5 mg/mL.

Quality Indicators

Good — use as normal

  • Clear, colorless solution

Acceptable

  • Very faint tint consistent across batch

Discard immediately

  • Cloudiness
  • Particulate
  • Discoloration

What to Expect

Weeks 1–8

GI side effects dominant early. Appetite suppression starts within first 2 weeks.

Weeks 9–24

Progressive weight loss, exceeding tirzepatide rates in Phase II data.

Weeks 25–48

Continued loss at slower rate; plateau at new lower set point.

Community Insights

Self-reported. Reflects user experience, not clinical outcomes.

Research References

Retatrutide, a GIP, GLP-1 & glucagon receptor agonist, for people with type 2 diabetes↗

The Lancet · 2023

Phase II: dose-dependent weight loss up to 24.2% at 12 mg. Significant HbA1c reduction.

doi:10.1016/S0140-6736(23)01053-X →

Verify what you have

Information on this page applies to pharmaceutical-grade peptides. Purity & identity of research-grade products vary. Certipep provides independent ESI-TOF-MS & HPLC analysis with a signed analytical report.

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