What it does
IGF-1 LR3 (Long Arginine-3 IGF-1) is a synthetic analog of insulin-like growth factor 1 modified to escape sequestration by IGF-binding proteins (IGFBPs). The N-terminal extension and Arg3 substitution dramatically reduce IGFBP-1, -3, and -5 binding, leaving more free IGF-1 in circulation and extending the functional half-life from minutes (native IGF-1) to ~20–30 hours. Originally developed as a research-grade tool for cell-culture work — and still primarily used for that purpose in legitimate science — it became a widely-circulated bodybuilding peptide claimed to drive hyperplastic muscle growth. Human clinical-trial evidence for body composition, strength, or healing in athletic populations is essentially absent. The risk profile, by contrast, is characterized: hypoglycemia from insulin-receptor cross-activation, theoretical (and oncologically relevant) sustained mitogenic signaling in any IGF-1R-expressing tissue, and the chronic-IGF-1-elevation safety concerns that apply to GH-secretagogue stacks at scale. Hold the line: the evidence is thin, the risks are real, and community framing is not evidence.
Used for
Dose
- Starting
- 20 mcg · once daily
- Common
- 50 mcg · once daily
- Upper
- 80 mcg · once daily
- When
- MorningDirect IGF-1 analog. Long half-life (~20–30 hours) makes precise timing less critical than for short-acting compounds, but morning dosing aligns with workout windows where IGF-mediated recovery signaling is most useful.
- Site
- subcutaneous (community)
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⚠ Caution
- Active or suspected malignancy (pre-existing cancer or strong family/personal cancer history) — IGF-1R agonism is mitogenic and should be considered contraindicated in this context
- Diabetes — IGF-1 LR3 cross-activates the insulin receptor and substantially increases hypoglycemia risk
- Pregnancy and breastfeeding
- Adolescents with open growth plates (use only under endocrinology supervision; recombinant IGF-1 in pediatric growth disorders is the appropriate context, not LR3)
- Concurrent use with insulin or insulin secretagogues without close glycemic monitoring
- Hypersensitivity to peptide formulations
Medications & conditions
- IGF-1-LR3 contraindicated in active malignancyExogenous IGF-1 administration is contraindicated in the setting of active cancer. IGF-1 is a potent mitogen; supraphysiologic levels accelerate proliferation across multiple tumor cell lines and may promote metastasis. Do not use IGF-1-LR3 during active oncology treatment or in patients with a personal history of malignancy without specialist review.
Often stacked with
- CJC-1295 — CJC-1295 raises endogenous GH (upstream); IGF-1 LR3 provides direct downstream IGF-1R agonism with extended half-life — serial pathway amplification, but timing and monitoring requirements differ.
Your stack
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