📖 Complete Guide✅ Updated 2026🔬 Evidence-Based

Retatrutide Guide

Eli Lilly

Complete guide to Retatrutide - the first triple agonist (GLP-1/GIP/Glucagon) showing up to 28.7% weight loss.

Last reviewed: March 2026

What Is Retatrutide?

Retatrutide (development code LY3437943) is Eli Lilly's investigational triple hormone receptor agonist. Unlike tirzepatide (Mounjaro/Zepbound) which targets two receptors, Retatrutide activates three: GLP-1, GIP, and Glucagon receptors.

Why glucagon? Adding glucagon receptor activation increases energy expenditure (calorie burning) and promotes fat breakdown in the liver. This third mechanism may explain the superior weight loss results compared to dual agonists.

Administration: Once-weekly subcutaneous injection, similar to Mounjaro and other GLP-1 medications.

The Triple Mechanism

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GLP-1 Agonism

Reduces appetite. Slows gastric emptying. Enhances insulin secretion. Same as Ozempic/Wegovy

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GIP Agonism

Enhances GLP-1 effects. Improves fat metabolism. Better glucose control. Same as Mounjaro/Zepbound

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Glucagon Agonism

Increases energy expenditure. Promotes fat burning. Reduces liver fat. Unique to Retatrutide

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Why This Matters

Most weight loss drugs only reduce calorie intake. Retatrutide's glucagon component also increases calorie burning, attacking obesity from both sides. This dual approach—eat less AND burn more—may exp

Phase 3 TRIUMPH-4 Results

Avg Weight Loss

28.7%

At the 12mg dose, participants lost an average of 28.7% of their body weight (approx. 71.2 lbs) over 68 weeks. This significantly outperforms Phase 2

Pain Reduction

75%

Retatrutide reduced WOMAC pain scores by approximately 75% (4.5 points), offering substantial relief for osteoarthritis patients. 1 in 8 patients were

High Response

58.6%

Beyond Weight Loss

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Liver Fat Reduction

Retatrutide showed remarkable effects on fatty liver disease (MASLD/MASH). In trials, participants achieved up to 86% reduction in liver fat content.

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Metabolic Improvements

Significant HbA1c reduction in diabetics. Improved blood pressure. Better lipid profiles. Reduced inflammation markers. Waist circumference reduction

Expected Dosing Schedule

Weeks 1-4

2mg weekly

Weeks 5-8

4mg weekly

Weeks 9-12

8mg weekly

Week 13+

12mg weekly

Side Effects

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Common (GI-Related)

Nausea (most common, dose-dependent). Diarrhea. Vomiting. Constipation. Decreased appetite

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Trial Observations

Glucagon effect: Unlike some concerns, the glucagon component did not raise blood sugar in trials. The GLP-1 and GIP components effectively counterbalanced any glucose-raising effects.

Development Timeline

2023:

Phase 2 results published in NEJM

December 11, 2025:

First positive Phase 3 TRIUMPH-4 readout announced

2026:

Additional TRIUMPH Phase 3 readouts expected across obesity and diabetes

Regulatory filing and launch timing depend on complete Phase 3 outcomes and revi — Regulatory filing and launch timing depend on complete Phase 3 outcomes and review

Vital Protocol FAQs

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Is Retatrutide better than Mounjaro?

Retatrutide's first Phase 3 readout showed very strong efficacy, but direct cross-trial comparisons to Mounjaro/Zepbound are imperfect because populations differ. Mounjaro/Zepbound are approved w

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Can I get Retatrutide now?

Retatrutide is not yet approved or available. It's currently in Phase 3 trials. Some research chemical suppliers may sell "research-grade" versions, but these are unregulated, potentially dangerous, a

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Will Retatrutide be expensive?

Pricing hasn't been announced, but expect it to be similar to or higher than Mounjaro/Zepbound ($1,000-1,500/month without insurance). Eli Lilly will likely price it as a premium next-generation thera

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What indications is Retatrutide being studied for?

Phase 3 trials are evaluating Retatrutide for obesity/overweight, Type 2 diabetes, and MASH (metabolic dysfunction-associated steatohepatitis, formerly NASH). It may receive multiple FDA approvals for

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