Inclusion of a compound does not constitute endorsement. Information sourced from published research and regulatory filings.

IGF-1 LR3

Category 1

Growth & Recovery · Research peptide (multiple suppliers)

Long-acting analog of IGF-1 with reduced IGFBP binding. Promotes muscle hyperplasia, protein synthesis, and glucose uptake. Monitor blood glucose closely due to insulin-like effects.

About

Mechanism

Long-acting analog of IGF-1 with an extended N-terminal peptide (arginine substitution at position 3 + 13-amino-acid extension). Reduced binding to IGF binding proteins (IGFBPs) results in longer half-life and greater bioavailability. Promotes muscle hyperplasia, protein synthesis, and glucose uptake in muscle tissue.

Half-Life

Approximately 20-30 hours (vs. 10-15 minutes for native IGF-1)

Route

subcutaneous

Frequency

Once daily (often post-workout)

Clinical Dosing

20-100 mcgonce daily (often post-workout)

Not FDA-approved. Not currently subject to Cat 2 restrictions.

Dosing extrapolated from animal studies and community protocols. No large-scale human clinical trials. Monitor blood glucose closely — can cause hypoglycemia.

Regulatory Status

FDA Category

Research peptide (not on FDA Category 2 list)

Reclassification

stable

Status based on publicly available FDA communications. Verify at FDA.gov for authoritative guidance.

View full regulatory timeline →

Titration Protocols

Research Dosing Protocol

Source: Community protocol based on Francis et al., Journal of Molecular Endocrinology, 1992

Dose	Duration	Draw (100 mcg vial in 1mL)	Notes
20 mcg	1 weeks	0.20 mL (20 units)	Starting dose to assess tolerance
50 mcg	Maintenance	0.50 mL (50 units)	Standard dose. Cycles: 4-8 weeks on, 4+ weeks off

Available Vial Sizes

0.1 mg

100 mcg vial

1 mg

1 mg vial

Citations

[1]Insulin-Like Growth Factor 1 with an Arg→Glu Substitution at Position 3 (Long R3 IGF-1) — Characterization. Journal of Molecular Endocrinology, 8(1), 29-38. Link(Reviewed: 2026-04-12)
[2]Anabolic Effects of IGF-1 and Long R3 IGF-1 in Animal Models. Growth Hormone & IGF Research, 8(S2), 123-127. Link(Reviewed: 2026-04-12)