Is IGF-1 LR3 the same as prescription IGF-1?

No. Prescription IGF-1 (mecasermin/Increlex) is FDA-approved for severe primary IGF-1 deficiency and is manufactured under strict quality controls. IGF-1 LR3 is a research chemical analog with no FDA approval, no human clinical data, and no manufacturing oversight. The LR3 modifications change its pharmacokinetics and potency in ways that have not been studied in humans.

Does IGF-1 LR3 cause cancer?

This is a theoretical concern but unproven in humans. IGF-1 is a growth factor that promotes cell proliferation, and epidemiological studies link high circulating IGF-1 levels to increased risk of prostate, breast, and colorectal cancer. Whether exogenous IGF-1 LR3 increases cancer risk is unknown because it has never been studied in humans. Anyone with a personal or family history of cancer should avoid IGF-1 analogs.

Content reviewed by clinical research staff

Last reviewed: March 2026Sources: PubMed, FDA, WADA Prohibited List

Evidence graded using the PeptideScholar A-D system

IGF-1 LR3

DLimited Data

Low Credibility

1 cited studyy · Evidence level D

Insulin-like growth factor-1 analog · 83 amino acids

Not FDA ApprovedWADA Banned

IGF-1 LR3 (Long R3 Insulin-like Growth Factor-1) is a synthetic analog of human IGF-1 with an arginine substitution at position 3 and a 13-amino-acid N-terminal extension. These modifications reduce binding to IGF-binding proteins, extending its half-life and increasing potency. It is sold as a research chemical and is popular in bodybuilding communities, though no human clinical data exists.

Mechanism of Action

Binds to the IGF-1 receptor (IGF1R) and insulin receptor with high affinity. The arginine substitution and N-terminal extension reduce binding to IGFBPs, increasing free circulating levels and tissue availability. This promotes cell proliferation, protein synthesis, and inhibits apoptosis. More potent than native IGF-1 in cell culture but unstudied in humans.

Benefits

Potent anabolic effects on muscle and bone in cell culture
Extended half-life vs native IGF-1 due to reduced IGFBP binding
Promotes cell survival and proliferation

Not Medical Advice — Research-Reported Information Only

This content is for informational purposes only and does not constitute medical advice.

IGF-1 LR3 — Dosing in Published Research

Reported Routes: Subcutaneous injection

No established human dosing. Research chemical suppliers recommend 20-100 mcg daily by subcutaneous injection, but this is not based on clinical data. The compound is not standardized or quality-controlled.

The dosing information above is sourced from published research literature and clinical trials. These are not recommendations. Individual responses vary. Always consult a healthcare provider before considering any peptide-based therapy.

Side Effects

No human safety data exists
Hypoglycemia risk (IGF-1 has insulin-like effects)
Theoretical cancer risk (IGF-1 is a growth factor for many tumor types)
Organomegaly and cardiac hypertrophy with chronic use (theoretical)
Not approved for human use; unregulated product quality

Considering Peptide Research?

IGF-1 LR3 is not FDA-approved. Always consult a licensed healthcare provider before considering any peptide.

Use the Peptide Finder

Always Consult a Professional

Research & Evidence

AnimalJ Surg Res, 2026

Provisional Treatment of Volumetric Muscle Loss With Insulin-like Growth Factor 1 Releasing Muscle Void Fillers.

IGF-1 releasing scaffolds supported muscle regeneration in volumetric muscle loss models

PMID: 41418663

References

1. Provisional Treatment of Volumetric Muscle Loss With Insulin-like Growth Factor 1 Releasing Muscle Void Fillers.. J Surg Res, 2026. “IGF-1 releasing scaffolds supported muscle regeneration in volumetric muscle loss models” [PMID: 41418663]

Recommended Resources

The Peptide Protocols Handbook

Evidence-based reference guide covering mechanisms, research, and clinical applications.

View on Amazon

Third-Party Peptide Testing

Independent lab analysis to verify peptide purity and authenticity.

Learn More

Links may be affiliate links. See our disclosure.

Research Supplies

Equipment for responsible research-grade peptide handling and administration.

Alcohol Prep Pads (200 ct)

Sterile 70% isopropyl pads for injection site preparation — essential for subcutaneous protocols.

$5–10View on Amazon

1mL Insulin Syringes (28G)

Thin-gauge 28G syringes for subcutaneous peptide administration with minimal discomfort.

$10–18View on Amazon

Sharps Disposal Container (1 Qt)

Biohazard-safe sharps container for responsible disposal of used syringes.

$8–15View on Amazon

Digital Milligram Scale (0.001g)

High-precision scale for accurate measurement of peptide powder before reconstitution.

$20–40View on Amazon

Amazon affiliate links — we may earn a small commission at no extra cost to you. See our disclosure.

IGF-1 LR3 FAQ

Medical Disclaimer

This content is for informational and educational purposes only and does not constitute medical advice, diagnosis, or treatment recommendations.

Always consult a qualified healthcare provider before starting, stopping, or modifying any treatment. Do not disregard professional medical advice based on information found on this site.

No claims of therapeutic efficacy are made for substances that are not FDA-approved for the discussed indications. Research citations reflect published findings and do not imply endorsement.

Related Peptides

Ipamorelin

Growth Hormone SecretagoguesNot Approved

Ipamorelin is a selective growth hormone secretagogue that stimulates growth hor...

Evidence Level BView Details

CJC-1295

Growth Hormone SecretagoguesNot Approved

CJC-1295 is a synthetic analog of growth hormone-releasing hormone (GHRH). Avail...