IGF-1 LR3 (Long R3 IGF-1) is a structurally modified analogue of insulin-like growth factor 1. Its modifications reduce binding to IGF-binding proteins, giving it a longer half-life and greater activity than native IGF-1. It is used as a research reagent, not an approved medicine.

What does research suggest about IGF-1 LR3?

In animal and cell-culture models, IGF-1 LR3 produces documented growth and metabolic effects through IGF-1 receptor agonism, which influences muscle and tissue growth. Human safety and efficacy data for the research-market form are lacking, so conclusions about its effects in people cannot reliably be drawn.

Is IGF-1 LR3 approved or legal?

IGF-1 LR3 is not an approved medicine for general use. It is sold and handled as a research chemical, and it is prohibited in competitive sport under anti-doping regulations. Its legal status varies by jurisdiction.

Its safety in humans is not established. As a potent growth factor it carries recognized and theoretical risks, and there is little human safety data. peptides.cx flags it as a higher-risk compound and does not present it as a validated or safe therapy.

What are the potential side effects of IGF-1 LR3?

Because it lowers blood sugar, hypoglycemia is a recognized risk. There are also theoretical concerns that stimulating cell proliferation could promote abnormal tissue growth. Its long-term side-effect profile in humans remains largely unknown.

How is IGF-1 LR3 different from regular IGF-1?

IGF-1 LR3 has an added N-terminal peptide extension and an amino-acid substitution that weaken its binding to IGF-binding proteins. This gives it a considerably longer half-life and stronger biological activity than natural IGF-1.

How does IGF-1 LR3 differ from the native IGF-1 used in approved medicine?

The LR3 version is a re-engineered analogue: it carries a 13-amino-acid extension on one end and a single amino-acid swap that make it bind poorly to the IGF-binding proteins that normally regulate and shorten native IGF-1's activity. The approved medicine mecasermin (Increlex) uses the unmodified native peptide instead. The two are not interchangeable, and the approval of native IGF-1 for a narrow condition does not extend to the LR3 form.

Why was Long R3 IGF-1 originally created if it was never meant as a drug?

It was primarily designed as a laboratory cell-culture reagent. Because it evades the binding proteins that quench native IGF-1, it keeps cells signalling for longer in a dish, which made it useful for research and bioproduction. Its later appearance in the physique and research-chemical scene was an off-label repurposing of a tool never intended for use in people.

Is IGF-1 LR3 the same thing as growth hormone?

No — this is a common misconception. Growth hormone (GH) acts partly by prompting the liver to release IGF-1, so the two are linked in the same axis, but they are distinct molecules with different receptors and effects. IGF-1 LR3 is a modified version of the downstream growth factor, not GH itself, and their risk and regulatory profiles are not the same.

Where can I buy IGF-1 LR3 and compare vendors?

Use the vendor comparison on this page. It shows only checked, product-specific links and identifies vendor claims, independent documentation and affiliate relationships separately. Availability and legal status can vary by country.

Growth Factor

Buy IGF-1 LR3 – Vendors, Prices, Testing and Evidence

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Also known as: Long R3 IGF-1

Evidence grade C — Early / PreclinicalRisk flag

Short answer

A long-acting IGF-1 analogue with significant hormonal/growth-factor risks and little human safety data.

Where can you buy IGF-1 LR3?

Crystal Peptides. The table lists only product-specific offers that were checked and for which a real destination exists. Missing prices, quantities, stock and laboratory details are not inferred.

What is known?

IGF-1 LR3 is a modified insulin-like growth factor 1 with extended half-life.

What is not established?

No approval for the research-market form; safety data is lacking.

Safety

Potent growth-factor with risks including hypoglycaemia and theoretical proliferative concerns. Not a validated therapy.

Regulatory status

Not an approved medicine for general use; prohibited in sport. Research chemical status.

Not medical advice. This educational reference is not diagnosis, treatment, prescribing, dosing or emergency guidance. Consult a qualified professional before making health-related decisions.

Regulatory or safety concern: This substance may be unapproved for human use, affect the hormonal system, or be subject to regulator or anti-doping restrictions. Check the cited evidence and rules in your jurisdiction.

Vendor comparison

Buy IGF-1 LR3: compare vendors

The table lists only product-specific offers that were checked and for which a real destination exists. Missing prices, quantities, stock and laboratory details are not inferred.

Vendor	Product	Documentation	Shipping	Checked	Action
Crystal Peptides Code PEPTIDES10 −10% · discount code details Sponsored	IGF-1 LR3 research product	Vendor-supplied data COA stated as available Not independently documented	Europe See the localized country store	Jul 18, 2026	View at vendor

Crystal Peptides

IGF-1 LR3 research product

Code PEPTIDES10 −10% · discount code details

What is it?

IGF-1 LR3 is a modified insulin-like growth factor 1 with extended half-life.

Research and evidence

IGF-1 LR3, also known as Long R3 IGF-1, is a modified version of insulin-like growth factor 1 (IGF-1), a naturally occurring hormone that plays a central role in growth, cell proliferation, and metabolism. The "LR3" designation reflects two structural changes: the addition of a 13-amino-acid extension at the N-terminus and a substitution at position three (arginine for glutamic acid). These modifications dramatically reduce the peptide's binding to IGF-binding proteins, which normally regulate and inactivate circulating IGF-1. The practical consequence is a substantially extended half-life and heightened biological activity compared with native IGF-1, which is why the molecule is studied and discussed primarily as a research reagent rather than a therapeutic product.

Interest in IGF-1 LR3 centers on the IGF-1 signaling pathway, which is a fundamental driver of tissue growth and repair. By acting as an agonist at the IGF-1 receptor, it influences pathways governing muscle protein synthesis, cellular proliferation, and glucose metabolism. Because of these effects, it is frequently discussed in the context of muscle repair and growth. However, it is important to distinguish the source of evidence: growth and metabolic effects have been documented in animal and cell-culture models, whereas robust human safety and efficacy data for the research-market form are lacking. There is no regulatory approval of IGF-1 LR3 as a medicine for general use, and it circulates as a research chemical rather than a validated therapy.

The honest evidence picture is one of significant unknowns paired with real, biologically plausible risks. As a potent growth factor, IGF-1 LR3 can lower blood sugar, creating a risk of hypoglycemia, and its stimulation of cell proliferation raises theoretical concerns about promoting the growth of abnormal tissue over the long term. Its long-term safety profile in humans is essentially uncharacterized. It is also prohibited in competitive sport under anti-doping rules. peptides.cx presents this information as an educational reference to help readers understand what the molecule is and where the science currently stands; it is not medical advice, and nothing here should be interpreted as guidance to obtain or use the compound.

Evidence grade: C

No approval for the research-market form; safety data is lacking. Growth and metabolic effects documented.

Human evidence

No approval for the research-market form; safety data is lacking.

Animal and preclinical evidence

Growth and metabolic effects documented.

Proposed mechanisms

IGF-1 receptor agonism affecting growth and metabolism

Safety concerns and known side effects

Potent growth-factor with risks including hypoglycaemia and theoretical proliferative concerns. Not a validated therapy.

Hypoglycaemia risk
Unknown long-term profile

Regulatory status

Not an approved medicine for general use; prohibited in sport. Research chemical status.

IGF-1 LR3 research timeline

1970s
Insulin-like growth factor 1 (originally called somatomedin C) is identified as a hormone that mediates many of growth hormone's effects on tissue growth and metabolism.
1980s
Recombinant human IGF-1 is produced, enabling laboratory study of the native growth factor and its interaction with IGF-binding proteins (IGFBPs).
early 1990s
Long R3 IGF-1 is engineered as a modified analogue — an extra 13-amino-acid N-terminal extension plus an Arg-for-Glu substitution at position 3 — designed largely as a cell-culture reagent that binds IGFBPs weakly and therefore stays active longer in vitro.
mid-2000s
Recombinant NATIVE IGF-1 (mecasermin, brand Increlex) gains regulatory approval for a rare paediatric growth-deficiency indication; this is the unmodified peptide, not the LR3 analogue, which was never developed as a medicine.
2000s–2020s
IGF-1 and its analogues are listed as prohibited substances in sport by anti-doping authorities; the LR3 form circulates on the research-chemical market with no approval and essentially no human safety data.

Frequently asked questions about IGF-1 LR3

What is IGF-1 LR3?: IGF-1 LR3 (Long R3 IGF-1) is a structurally modified analogue of insulin-like growth factor 1. Its modifications reduce binding to IGF-binding proteins, giving it a longer half-life and greater activity than native IGF-1. It is used as a research reagent, not an approved medicine.
What does research suggest about IGF-1 LR3?: In animal and cell-culture models, IGF-1 LR3 produces documented growth and metabolic effects through IGF-1 receptor agonism, which influences muscle and tissue growth. Human safety and efficacy data for the research-market form are lacking, so conclusions about its effects in people cannot reliably be drawn.
Is IGF-1 LR3 approved or legal?: IGF-1 LR3 is not an approved medicine for general use. It is sold and handled as a research chemical, and it is prohibited in competitive sport under anti-doping regulations. Its legal status varies by jurisdiction.
Is IGF-1 LR3 safe?: Its safety in humans is not established. As a potent growth factor it carries recognized and theoretical risks, and there is little human safety data. peptides.cx flags it as a higher-risk compound and does not present it as a validated or safe therapy.
What are the potential side effects of IGF-1 LR3?: Because it lowers blood sugar, hypoglycemia is a recognized risk. There are also theoretical concerns that stimulating cell proliferation could promote abnormal tissue growth. Its long-term side-effect profile in humans remains largely unknown.
How is IGF-1 LR3 different from regular IGF-1?: IGF-1 LR3 has an added N-terminal peptide extension and an amino-acid substitution that weaken its binding to IGF-binding proteins. This gives it a considerably longer half-life and stronger biological activity than natural IGF-1.
How does IGF-1 LR3 differ from the native IGF-1 used in approved medicine?: The LR3 version is a re-engineered analogue: it carries a 13-amino-acid extension on one end and a single amino-acid swap that make it bind poorly to the IGF-binding proteins that normally regulate and shorten native IGF-1's activity. The approved medicine mecasermin (Increlex) uses the unmodified native peptide instead. The two are not interchangeable, and the approval of native IGF-1 for a narrow condition does not extend to the LR3 form.
Why was Long R3 IGF-1 originally created if it was never meant as a drug?: It was primarily designed as a laboratory cell-culture reagent. Because it evades the binding proteins that quench native IGF-1, it keeps cells signalling for longer in a dish, which made it useful for research and bioproduction. Its later appearance in the physique and research-chemical scene was an off-label repurposing of a tool never intended for use in people.
Is IGF-1 LR3 the same thing as growth hormone?: No — this is a common misconception. Growth hormone (GH) acts partly by prompting the liver to release IGF-1, so the two are linked in the same axis, but they are distinct molecules with different receptors and effects. IGF-1 LR3 is a modified version of the downstream growth factor, not GH itself, and their risk and regulatory profiles are not the same.
Where can I buy IGF-1 LR3 and compare vendors?: Use the vendor comparison on this page. It shows only checked, product-specific links and identifies vendor claims, independent documentation and affiliate relationships separately. Availability and legal status can vary by country.

Common discussion areas

IGF pathwayRisk profile

Compare IGF-1 LR3

IGF-1 LR3 vs MGF / PEG-MGF

Sources

Editorial review and transparency

Written by: peptides.cx Editorial Team
Scientific reviewer: No named medical reviewer is currently assigned
Last editorial review: June 1, 2026
Last vendor check: July 18, 2026
Review method: Source review, claim verification, vendor-data separation and regulatory-context review.
Commercial disclosure and conflicts: Vendor relationships do not determine evidence or safety ratings. No named reviewer conflict is recorded because no named reviewer is assigned.

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