IGF-1 LR3
Also known as: Long R3 IGF-1, LR3, Long Arg3 IGF-1
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Key Facts: IGF-1 LR3
- Category
- Growth Hormone
- FDA Status
- Not FDA Approved
- Clinical Status
- Not approved for human use anywhere. Sold as a laboratory reagent and as a research chemical. Banned in sport under WADA rules.
- Administration
- Subcutaneous injection. Because of the hypoglycemia risk, timing relative to carbohydrate intake is the main practical consideration reported.
- Typical Dose
- 20-50 mcg daily
- Frequency
- Once daily
- Duration
- Community cycles are typically reported as 4-6 weeks, on the reasoning that receptor downregulation follows longer use
Mechanism of Action
Natural IGF-1 is almost entirely bound up by IGF binding proteins in circulation, which controls how much is active and gives it a half-life measured in minutes. LR3 makes two changes: an arginine substitution at position 3, and a 13-amino-acid extension on the N-terminus. Together these dramatically reduce binding-protein affinity, so far more of the molecule stays free and active, extending the functional half-life to something on the order of a day rather than minutes. Once free, it activates the IGF-1 receptor, driving protein synthesis, satellite cell activation and cell proliferation in muscle. That same lack of binding-protein regulation is the reason for caution: binding proteins are a control mechanism, and removing the control is the point of the drug and also its main risk.
Research Summary
IGF-1 LR3 was developed as a cell culture reagent, and that remains its principal legitimate use: it is sold to laboratories to promote cell growth in bioreactors. There are no published randomized human trials of IGF-1 LR3 for muscle growth, body composition or performance. The animal and in vitro work does show what you would expect, increased protein synthesis and muscle cell proliferation, and there is a genuine human literature on recombinant IGF-1 (mecasermin) for severe IGF-1 deficiency, but mecasermin is a different molecule with different pharmacokinetics and its trial data should not be read across. The two consistent safety themes in the underlying biology are hypoglycemia, because IGF-1 has meaningful cross-reactivity with the insulin receptor, and the theoretical concern that chronically elevated IGF-1 signalling promotes growth of tissue you did not intend to grow, including existing tumors.
Dosing Information
Note: Animal study doses may not translate directly to humans.
Typical Dosingⓘ
Community experience
20-50 mcg daily
20-50 mcg daily (community reported)
Once daily
There is no clinical dosing standard because there are no clinical trials. Hypoglycemia is the risk that most often requires medical attention with this compound, and community reports consistently describe it coming on quickly.
Research Dosingⓘ
Scientific studies
Community-reported only. No clinical dosing exists for this analog.
Doses from Studies
20-50 mcg daily
Community-reported protocols - No clinical trials of this analog exist. This range is user-reported only.
Duration
Community cycles are typically reported as 4-6 weeks, on the reasoning that receptor downregulation follows longer use
Administration
Subcutaneous injection. Because of the hypoglycemia risk, timing relative to carbohydrate intake is the main practical consideration reported.
Timing & Administration
Best Time to Take
With or near a carbohydrate-containing meal
Once daily in most reported protocols
Food Recommendation
Take with food
Why This Timing?
The dominant acute risk is hypoglycemia. Community protocols consistently pair dosing with food for that reason.
Possible Side Effects
Not everyone experiences these effects. Individual responses vary based on dosage, duration, and personal factors.
- ●Hypoglycemia, the most immediate and serious risk
- ●Hunger and lightheadedness as early hypoglycemia signs
- ●Injection site reactions and localized tissue growth
- ●Joint pain
- ●Theoretical promotion of existing tumor growth with sustained elevated IGF-1 signalling
- ●Long-term safety in humans is entirely uncharacterized
References
- https://pubmed.ncbi.nlm.nih.gov/?term=IGF-1+LR3+long+R3
- https://pubmed.ncbi.nlm.nih.gov/?term=insulin-like+growth+factor+1+binding+protein+analog
- https://pubmed.ncbi.nlm.nih.gov/?term=IGF-1+signaling+cancer+risk+review
Research This Peptide Further
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IGF-1 LR3 from $53/kit
5 verified vendors, ≥99% purity, COAs included.
Frequently Asked Questions
What does IGF-1 LR3 do?
IGF-1 LR3 is a modified version of insulin-like growth factor 1, engineered to last far longer in the body than the natural hormone. It is popular in physique circles and it is worth being blunt about the evidence: there are effectively no human clinical trials of this specific analog. Everything below the mechanism section is preclinical work, laboratory use, or community reporting.
How does IGF-1 LR3 work?
Natural IGF-1 is almost entirely bound up by IGF binding proteins in circulation, which controls how much is active and gives it a half-life measured in minutes. LR3 makes two changes: an arginine substitution at position 3, and a 13-amino-acid extension on the N-terminus. Together these dramatically reduce binding-protein affinity, so far more of the molecule stays free and active, extending the functional half-life to something on the order of a day rather than minutes. Once free, it activates the IGF-1 receptor, driving protein synthesis, satellite cell activation and cell proliferation in muscle. That same lack of binding-protein regulation is the reason for caution: binding proteins are a control mechanism, and removing the control is the point of the drug and also its main risk.
Is IGF-1 LR3 FDA approved?
No, IGF-1 LR3 is not currently FDA approved. Current status: Not approved for human use anywhere. Sold as a laboratory reagent and as a research chemical. Banned in sport under WADA rules.
What are the side effects of IGF-1 LR3?
Reported side effects include: Hypoglycemia, the most immediate and serious risk, Hunger and lightheadedness as early hypoglycemia signs, Injection site reactions and localized tissue growth, Joint pain, Theoretical promotion of existing tumor growth with sustained elevated IGF-1 signalling. Individual responses vary based on dosage, duration, and personal health factors.
What is the typical dose of IGF-1 LR3?
Community-reported common dose: 20-50 mcg daily (Once daily). Range: 20-50 mcg daily (community reported). Administration: Subcutaneous injection. Because of the hypoglycemia risk, timing relative to carbohydrate intake is the main practical consideration reported.. Community-reported doses. Not medical advice. Consult healthcare provider.
Related Peptides
Peptides commonly compared with IGF-1 LR3 or used in similar applications.
Ipamorelin
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FDAHuman growth hormone is the real thing rather than a secretagogue: a 191-amino-acid protein identical to what your pituitary makes, produced recombinantly since the 1980s. It is a properly approved medicine for growth hormone deficiency, and it is also the most misused compound in this entire space. Almost everything you read about HGH for anti-aging or physique traces back to a single small 1990 study whose own author later disowned how it was used.
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Clinical TrialsCJC-1295 is a synthetic analog of growth hormone-releasing hormone (GHRH), specifically a modified GHRH(1-29), engineered for a long duration of action. The form most people mean by CJC-1295 includes a Drug Affinity Complex (DAC) that binds blood albumin to extend its half-life to roughly 6 to 8 days, raising GH and IGF-I for days from a single injection. It was developed by ConjuChem, reached Phase II trials and was abandoned; it is not an approved drug and is sold only as a research chemical. A version without DAC (Modified GRF 1-29) acts for only about 30 minutes.
Growth HormoneTesamorelin
FDATesamorelin is a stabilized analog of growth-hormone-releasing hormone (GHRH 1-44) with a chemical modification that protects it from rapid breakdown. It is FDA-approved (brand name Egrifta) to reduce excess visceral abdominal fat in people with HIV-associated lipodystrophy, which makes it one of the few growth-hormone-axis peptides with a real approval behind it. Its evidence base is solid for that specific population and thinner for the general anti-aging and fat-loss uses it gets promoted for online.
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Clinical TrialsGHRP-6 is a synthetic six-amino-acid peptide (His-D-Trp-Ala-Trp-D-Phe-Lys-NH2) that tricks the body into releasing its own growth hormone. It was one of the first growth hormone secretagogues ever made, and the hunt to find out why it worked led scientists straight to the discovery of ghrelin. It has no approval as a drug anywhere and is used only as a research compound.
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