Retatrutide Dosage for Weight Loss: The Complete 2026 Guide

Retatrutide (marketed as "triple agonist") is generating excitement as one of the most powerful weight loss peptides in development. As a once-weekly triple agonist targeting GLP-1, GIP, and glucagon receptors, it produces significantly greater weight loss than dual agonists like tirzepatide.

This guide covers the latest dosing protocols based on clinical trial data from Eli Lilly's Phase 2 and Phase 3 trials.

Understanding Retatrutide

Retatrutide is an investigational once-weekly triple hormone receptor agonist that targets:

• GLP-1 (Glucagon-like peptide-1) — Appetite suppression, glucose control
• GIP (Glucose-dependent insulinotropic polypeptide) — Enhanced metabolic effects
• Glucagon — Increased energy expenditure, fat burning

By targeting all three receptors, retatrutide produces synergistic effects that surpass even tirzepatide (dual agonist) in clinical trials.

Clinical Trial Dosing Data

Phase 2 Trial Results

In the landmark Phase 2 trial published in the New England Journal of Medicine, participants received escalating doses over 48 weeks:

• Weeks 1-4: 1 mg weekly
• Weeks 5-8: 2 mg weekly
• Weeks 9-12: 4 mg weekly
• Weeks 13-24: 6 mg weekly
• Weeks 25-48: 8 mg weekly (or 12 mg in higher-dose group)

Phase 3 Trial Results (TRIUMPR-1)

The latest Phase 3 trial tested higher doses with impressive results:

• 9 mg weekly — Average 24.2% weight loss (71.2 lbs in some participants)
• 12 mg weekly — Similar results to 9mg with slightly higher response rates
• 4 mg maintenance — Tested as maintenance dose for long-term sustainability

Typical Dosing Protocol

Based on clinical trial data, here's the recommended titration schedule for research purposes:

Standard Titration Schedule

Conservative Protocol (For Sensitive Individuals)

• Week 1-2: 0.25 mg (if available)
• Week 3-4: 0.5 mg
• Week 5-6: 1 mg
• Week 7-8: 2 mg
• Week 9-12: 4 mg
• Week 13+: Adjust based on response and tolerance

Weight Loss Expectations

Based on clinical trial data, here's what you can expect:

Results vary based on diet, exercise, starting weight, and individual response.

Side Effects & Safety

Retatrutide's side effects are similar to other GLP-1 agonists but may be more pronounced due to the triple mechanism:

Common Side Effects

• Nausea — Most common, especially during dose escalation
• Vomiting — Usually mild to moderate
• Diarrhea — Often subsides over time
• Constipation — Less common than with other GLP-1s
• Abdominal pain — Generally mild
• Fatigue — Especially in first few weeks

Less Common but Serious

• Pancreatitis (rare)
• Gallbladder issues (rare)
• Thyroid C-cell tumors (observed in rodents, not confirmed in humans)

Managing Side Effects

• Stay well hydrated
• Eat smaller, more frequent meals
• Avoid high-fat foods during titration
• Start low and go slow — Conservative titration minimizes GI issues
• Take anti-nausea medication if needed — Consult your provider

Retatrutide vs Other GLP-1s

Important Considerations

• Retatrutide is investigational — Not FDA approved yet (as of early 2026)
• Phase 3 trials ongoing — Full approval expected 2026-2027
• Research compound only — Should only be used under medical supervision
• Diet and exercise matter — Best results combined with caloric deficit and regular exercise
• Monitor for gall bladder issues — Ultrasound recommended every 6-12 months
• Protein intake crucial — Aim for 1.2-1.6g protein per kg body weight

Where to Learn More

• Check out our Peptide Calculator for dosing calculations
• Compare peptides in our Peptide Comparison Tool
• Explore community protocols in The Lab

Conclusion

Retatrutide represents a significant advancement in obesity treatment, offering nearly 25% weight loss at the highest doses. The typical therapeutic dose ranges from 4-12mg weekly, with most protocols recommending gradual titration to minimize side effects.

As an investigational compound, retatrutide should only be obtained and used under proper medical supervision. The Phase 3 TRIUMPR trials are ongoing, with full FDA approval expected in late 2026 or 2027.

For those seeking weight loss support, semaglutide and tirzepatide remain FDA-approved options, while retatrutide offers promising results for those participating in clinical trials or accessing through research channels.