IGF-1 LR3 (also known as IGF-1 LR3 or Long R3 IGF-1 or Long Arg3 IGF-1) is a performance-enhancing peptide studied for its effects on muscle gain, recovery, growth hormone. Synthetic long-acting IGF-1 analog, ~3x potency, 20-30 hour half-life. Boosts muscle growth and tissue repair. Not FDA-approved, significant risks.
IGF-1 LR3 (Long Arg3 Insulin-Like Growth Factor-1) is a synthetic 83-amino acid analog of human insulin-like growth factor-1 (IGF-1), engineered with an arginine substitution at position 3 and an additional 13 amino acids at the N-terminus. These structural modifications significantly reduce its binding affinity to IGF-binding proteins (IGFBPs), resulting in an extended half-life of approximately 20-30 hours (compared to native IGF-1's ~10 minutes) and roughly three times greater biological potency than endogenous IGF-1. The peptide functions by binding to IGF-1 receptors (IGF-1R) on various cell types, initiating complex intracellular signaling cascades through the PI3K/Akt and MAPK/ERK pathways that promote cellular proliferation, differentiation, protein synthesis, and cell survival while inhibiting apoptosis.
Overview
IGF-1 LR3 has been extensively studied in preclinical research for its powerful anabolic effects, including stimulation of muscle hypertrophy through satellite cell activation, enhanced nitrogen retention and protein synthesis, accelerated tissue repair and regeneration, improved fat metabolism and lean mass development, potential neuroprotective effects through neurogenesis and synaptic plasticity, and metabolic benefits through enhanced glucose uptake in muscle and adipose tissue.
Due to its structural similarity to insulin, it also demonstrates some insulin-like metabolic effects.
However, IGF-1 LR3 carries significant risks including hypoglycemia (especially with continuous high dosing), potential increased cancer risk due to cellular proliferation effects, muscle and joint pain, and other side effects.
It is not FDA-approved for therapeutic use, is classified as a prohibited substance by the World Anti-Doping Agency (WADA), and remains strictly designated for research purposes only.
The compound requires careful handling, proper reconstitution with bacteriostatic water, and refrigerated storage.
Mechanism of action
Powerfully increases muscle growth, protein synthesis, and fat burning. Accelerates tissue repair and recovery. Risk of hypoglycemia.
Reported effects
Effects reported in the literature and from preclinical models include:
- Controlled release of IGF-1 LR3 from a decellularized plant-based nerve conduit significantly improved axonal regeneration in a rat sciatic nerve defect, matching autologous graft performance without inducing systemic toxicity [1] Preclinical
- A one-week IGF-1 LR3 infusion into growth-restricted fetal sheep did not improve fetal growth and reduced circulating amino acids, notably branched-chain amino acids [2] Preclinical
- In people self-administering IGF-1 LR3 and related GH-IGF-1 axis peptides, reported adverse effects include endocrine-metabolic disturbances such as dysglycaemia, fluid retention, musculoskeletal myalgia and arthralgia, and injection-site reactions [3] Anecdotal
- Peer-reviewed human evidence for IGF-1 LR3's putative performance and body-recomposition benefits is absent, and its mitogenic cancer-risk concerns remain biologically plausible but unproven [3] Anecdotal
Evidence grades: FDA approved Phase III Phase II Phase I Preclinical Anecdotal
Dosage and administration
Research Beginner
- 20-40mcg daily, typically post-workout
Research Intermediate
- 40-60mcg daily, split into 1-2 doses
Research Advanced
- 60-100mcg daily, split into 2 doses
General
- Intramuscular or subcutaneous injection
- Often injected bilaterally into muscles being trained
- Minimum 4-6 week break between cycles recommended
- Reconstitute with bacteriostatic water or acetic acid
- Store reconstituted solution at 2-8°C, use within 14-30 days
Cycle length
- typically 4-6 weeks maximum
Post
- workout timing common due to enhanced nutrient uptake
Natty status
IGF-1 LR3 is classified as not natty. It appears on the WADA prohibited list and is banned by major natural bodybuilding federations.[4] Use of this compound places the athlete in the enhanced category rather than the natural category in competitive contexts.
Research
The peptide has been the subject of 4 studies and reference works collected on this site. The full bibliography is in § External links below.
Related compounds
Other peptides in this catalogue with overlapping mechanisms or status:
References
- ^ Revolutionary decellularized Alstroemeria stem-based nerve conduit integrated with GelMA and controlled IGF-1 LR3 release for enhanced rat sciatic nerve regeneration. Recent
- ^ IGF-1 LR3 does not promote growth in late-gestation growth-restricted fetal sheep. Recent
- a b The emerging landscape of performance-enhancing peptides modulating GH-IGF1 axis: bridging the gap between clinical evidence and patient self-administration. Recent review
- a b World Anti-Doping Agency. (2026). Prohibited List 2026.
External links
- Wikipedia article
- 1mg IGF-1 LR3 — commercial
- Bacteriostatic Water Reconstitution Solution 10ml — commercial
This page was last updated on July 17, 2026, at 16:22 (UTC).
Research last reviewed on July 17, 2026.
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