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Triple Incretin Agonist / GLP-1 Receptor Agonist

Retatrutide (GLP-1/GIP/Glucagon Triple Agonist)

A once-weekly injectable peptide that simultaneously activates GLP-1, GIP, and glucagon receptors — producing greater fat loss than semaglutide or tirzepatide while preserving lean mass better than single-agonist agents. Currently in Phase 3 trials (Eli Lilly).

metabolicfat-losshormonal-optimization
Tier B— Generally safe — moderate evidence
Evidence gradeB — Controlled trials / Cohort studies
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Reviewed & fact-checked by

BiohackingHub Research Team

Editorial Research Team · Last updated: March 26, 2026

Verified

What Makes Retatrutide Different

Unlike semaglutide (GLP-1 only) or tirzepatide (GLP-1/GIP dual), retatrutide is a triple agonist — simultaneously activating:

  • GLP-1 receptors — appetite suppression, slowed gastric emptying, improved insulin secretion
  • GIP receptors — enhanced insulin sensitivity, fat cell signalling, reduced GLP-1 side effects
  • Glucagon receptors — direct hepatic fat oxidation, increased energy expenditure

The glucagon component is the key differentiator. Glucagon receptor activation drives liver fat clearance and increases thermogenesis — effects absent in semaglutide and only partially present in tirzepatide.

Phase 2 Clinical Data

The NEJM Phase 2 trial (2023) enrolled 338 adults with obesity (BMI ≥27) across multiple doses over 48 weeks: []

| Dose | Mean Weight Loss | |------|-----------------| | 4 mg/week | 8.7% | | 8 mg/week | 17.1% | | 12 mg/week | 22.8% | | 24 mg/week | 24.2% |

At 24mg/week, retatrutide produced 24.2% mean body weight reduction — approximately double the efficacy of semaglutide 2.4mg (Wegovy) in comparable populations.

Lean Mass Preservation

The glucagon component raises a concern: glucagon is catabolic and can drive muscle protein breakdown at high levels. Phase 2 data showed approximately 10% of weight lost was lean mass — similar to semaglutide but better than expected given the glucagon component. Combining with resistance training and GH secretagogues (ipamorelin + CJC-1295) is strongly recommended.

Titration Protocol

Slow titration is essential to manage GI side effects:

  • Weeks 1–4: 2mg/week
  • Weeks 5–8: 4mg/week
  • Weeks 9–12: 8mg/week
  • Maintenance: 8–12mg/week (most users do not need 24mg)

⚕ Phase 3 trials ongoing. Not FDA/EMA approved. Access through compounding pharmacies requires physician oversight. Long-term safety data beyond 48 weeks is limited.

Stacking Interactions

How Retatrutide (GLP-1/GIP/Glucagon Triple Agonist) interacts with other compounds

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IpamorelinSynergisticweak evidence

The key lean mass preservation stack. Take ipamorelin 100–200mcg before bed. Monitor protein intake (minimum 1.6g/kg lean mass).

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CJC-1295 (without DAC)Synergisticweak evidence

Use CJC-1295 + ipamorelin combination alongside retatrutide for lean mass preservation protocol.

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Berberine (Liposomal)Synergisticweak evidence

Take berberine with meals. May allow slower retatrutide titration while maintaining glycaemic benefits.

Safety Profile — Tier B

Generally safe — moderate evidence

Contraindications

  • ●Personal or family history of medullary thyroid carcinoma (MTC)
  • ●Multiple Endocrine Neoplasia syndrome type 2 (MEN 2)
  • ●Active pancreatitis
  • ●Severe gastroparesis
  • ●Pregnancy or breastfeeding

Side Effects

  • ●Nausea (most common, especially during dose escalation — 40–60% of users)
  • ●Vomiting and diarrhoea during titration
  • ●Decreased appetite (desired in fat loss context)
  • ●Injection site reactions
  • ●Potential lean mass loss without resistance training (mitigated by protein intake + GH peptides)

Drug Interactions

Insulin and sulfonylureas — hypoglycaemia risk, dose reduction requiredOral medications with narrow therapeutic windows — delayed gastric emptying affects absorption

Research References

  1. [1]PubMed: 37216658
  2. [2]PubMed: 38048249