How does IGF-1 LR3 work?
Long Arg3 IGF-1, a modified IGF-1 with arginine at position 3 and an N-terminal extension. Resists binding to IGFBPs (which normally sequester IGF-1), giving it ~3x longer half-life and stronger systemic activity than native IGF-1. In plain terms, IGF-1 LR3 is used to drive muscle growth. A long-acting form of insulin-like growth factor 1, with limited human safety data and a real side effect profile, handle with discipline. Mechanistic detail like this comes largely from preclinical and early research, the human picture is limited.
What people use it for
- Experienced users who already have GH-axis baseline
- Short, focused anabolism cycles
References
- IGF-I and its analogs in clinical use — Clemmons DR, Endocrinol Metab Clin North Am, 2012
- Detection of His-tagged Long-R3-IGF-I in a black market product — Kohler M, Thomas A, Walpurgis K, et al., Growth Hormone & IGF Research, 2010
- Site-specific fluorescent derivatization and liquid chromatographic-mass spectrometric characterization of long R(3) IGF-I for bioanalytical applications — Harvey MD, Banks PR, Journal of Chromatography B, 2003
Pepdex is an editorial reference, not medical advice. Peptides vary in legal and approval status by country, many are research compounds without full human safety data. Talk to a qualified clinician before starting anything.
More on IGF-1 LR3
Last updated 2026-06-06.