IGF-1 LR3
Growth Factor AnalogresearchAlso known as: Long R3 IGF-1, Long Arginine 3-IGF-1, LR3-IGF-1
A modified version of insulin-like growth factor 1 with an extended half-life, potently promoting muscle growth, hyperplasia, and recovery through direct anabolic signaling.
Overview
IGF-1 LR3 (Long R3 Insulin-like Growth Factor 1) is a modified analog of human IGF-1 with 83 amino acids (vs. 70 in native IGF-1). The modification includes an arginine substitution at position 3 and a 13-amino acid N-terminal extension, which dramatically reduces binding to IGF binding proteins (IGFBPs). This results in a much longer half-life (~20-30 hours vs. ~15 minutes for native IGF-1) and greater bioavailability. IGF-1 LR3 is one of the most potent anabolic peptides available, capable of promoting both muscle hypertrophy (cell enlargement) and hyperplasia (new cell creation). It is widely used in bodybuilding and performance communities for its ability to increase lean mass, accelerate recovery, and promote fat loss. However, it carries significant risks including hypoglycemia and potential tumor growth stimulation.
Mechanism of Action
IGF-1 LR3 binds to the IGF-1 receptor (IGF-1R) with high affinity while evading sequestration by IGF binding proteins: (1) Activates PI3K/Akt/mTOR pathway to stimulate protein synthesis and muscle hypertrophy; (2) Promotes satellite cell activation and differentiation, enabling muscle hyperplasia (new fiber formation); (3) Inhibits protein degradation through suppression of FOXO transcription factors and ubiquitin-proteasome pathway; (4) Enhances glucose and amino acid uptake into muscle cells; (5) Promotes fat oxidation by redirecting nutrient partitioning toward muscle; (6) Stimulates collagen and cartilage synthesis; (7) Extended half-life allows systemic rather than just local effects.
Molecular Formula
C400H625N111O115S9
Molecular Weight
9111.4 g/mol
Sequence
83-amino acid modified IGF-1 with N-terminal extension and Arg3 substitution
Dosage Protocols
Dose Range
20mcg – 50mcg
Frequency
Once daily
Route
subcutaneous or intramuscular
Cycle Length
4-6 weeks on, 4 weeks off
Inject post-workout into the muscle trained or subcutaneously. Start at lower dose. Must monitor blood glucose levels. Have fast-acting carbs available for hypoglycemia.
Source: Community protocols
🧮 Personalized Dosage Calculator
💰 Estimated Pricing
Typical Supply
1mg vial
Last Updated
2026-02
Long-acting IGF-1 variant. Research: $40-100/mg. Popular in bodybuilding. Longer half-life than native IGF-1.
⚠️ Prices are estimates based on publicly available data and may vary significantly by vendor, location, and prescription status. This is not medical or financial advice.
Side Effects
| Effect | Severity |
|---|---|
| Hypoglycemia | severe |
| Joint pain | moderate |
| Gut distension | moderate |
| Water retention | mild |
| Potential tumor growth | severe |
| Injection site pain | mild |
Pros & Cons
One of the most potent anabolic peptides — promotes both muscle hypertrophy and hyperplasia
Extended half-life (20-30 hours) provides sustained anabolic signaling
Promotes satellite cell proliferation for true new muscle fiber creation
Enhances nutrient partitioning — directs calories toward muscle rather than fat
Significant hypoglycemia risk requires careful carbohydrate management
Potential to stimulate growth of pre-existing tumors or cancer cells
Prolonged use may cause organ growth including intestinal hypertrophy (GH gut)
Illegal in many jurisdictions and banned in all competitive sports
Short cycle requirements limit long-term benefits
Research Studies
🩸 Blood Work
IGF-1
Exogenous IGF-1 — must monitor total levels to avoid excess
Fasting Blood Glucose
IGF-1 has insulin-like effects — can cause hypoglycemia
Fasting Insulin
IGF-1 affects insulin signaling pathways
HbA1c
Long-term glucose monitoring with insulin-like peptide
Liver Function Panel (AST/ALT)
IGF-1 is primarily produced by the liver
CBC (Complete Blood Count)
IGF-1 promotes cell proliferation
Long-acting IGF-1 analog (extended half-life via LR3 modification). Potent growth factor with hypoglycemia risk. Elevated IGF-1 levels are associated with increased cancer risk. Must monitor carefully.
Legal Status
Not FDA-approved. Available as a research chemical. Banned by WADA. Classified as a controlled substance in some jurisdictions. Subject to strict regulation in many countries.
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