Growth Hormone & IGF Axis
IGF-1 LR3 (Long R3 IGF-1)
Commonly used for
Muscle GrowthRecoveryMuscle & Strength
What is it?
IGF-1 LR3 (Long R3 IGF-1) is a modified analogue of insulin-like growth factor-1 engineered for markedly reduced affinity for IGF-binding proteins, which increases its bioavailability and biological activity compared to native IGF-1.
Mechanism of action: IGF-1 receptor agonist; Markedly reduced IGF-binding-protein affinity, increasing bioavailability and biological activity; Stimulates protein synthesis in skeletal muscle (preclinical/pharmacologic)
What do people use it for?
Proposed indications: IGF-1 replacement (research); Muscle protein synthesis (preclinical); Recovery
How is it used? / Dosing
Commonly reported by peptide clinics†: 20-50 mcg/day, subcutaneous
Bodybuilding/research-chemical community sources commonly report 20-50 mcg/day by subcutaneous injection, often into recently-trained muscle. No human clinical trials exist for this analog at this dose -- this reflects community convention, not evidence.
†Reported by peptide clinics and compounding pharmacies -- not derived from human clinical trials. Not an individualized recommendation. Actual use should be supervised by a qualified provider.
Typical clinical dosing schedule: No established clinical dosing. Not an approved therapeutic agent; used in laboratory/research settings only.
Administration: Subcutaneous or intramuscular injection (research settings) — No established clinical dosing
How does it compare?
Compare with:
How well does it work? / Evidence
? Emerging / limited evidence
An "emerging / limited evidence" rating means rigorous research hasn't caught up yet -- not that this peptide doesn't work. Many peptides in this category are newer or simply understudied rather than proven ineffective.
Evidence rating: ⭐⭐⭐☆☆ — Well-characterized in laboratory/pharmacologic research as a long-acting IGF-1 analogue; human clinical trial data for therapeutic or performance use are lacking.
Safety & side effects
Common side effects: Injection-site reactions, Hypoglycemia (insulin-like effect)
Serious risks: Hypoglycemia risk; Theoretical concern for stimulating malignant cell growth given IGF-1 pathway activity; Unknown long-term safety
Drug interactions: May potentiate hypoglycemia when combined with insulin or other glucose-lowering therapies.
Monitoring: Blood glucose, Clinical adverse effects
Legal & regulatory status
Legal status: Not FDA-approved for human use. This is a research compound, not a medication — any use should only occur under the direction of a licensed healthcare provider, and its legal availability varies and changes frequently. Verify current status independently before considering use.
Regulatory status: Research peptide • Not FDA approved
Who should avoid it?
Contraindications: Not established. Avoid in:; Pregnancy; Active malignancy (IGF-1 pathway activation is a theoretical concern in cancer biology); Uncontrolled endocrine disease
Pregnancy & breastfeeding: Avoid.