IGF-1 LR3
INVESTIGATIONALLong-acting insulin-like growth factor
By the INFOPEPTIDOS editorial team · content based on scientific literature.
Updated: August 2026.
Key points
- What it is: long-acting analog of insulin-like growth factor 1 (IGF-1).
- Main use: muscle growth, recovery and hyperplasia (new muscle cells).
- Typical dose: 20–50 mcg once a day, subcutaneous injection.
- Key result: potent anabolic stimulus; its long half-life extends the IGF-1 signal.
- Common effects: hypoglycemia, swelling and digestive discomfort.
- Comparison: acts downstream of GH; secretagogues raise GH, IGF-1 LR3 delivers the final signal.
- Status: not FDA-approved (research compound).
Overview
What is IGF-1 LR3?
IGF-1 LR3 is a modified version of insulin-like growth factor 1 (IGF-1), the hormone through which growth hormone exerts many of its anabolic effects. The 'Long R3' modification reduces its binding to carrier proteins, which markedly extends its half-life and action.
Key benefits
Direct anabolic stimulus of muscle: protein synthesis, recovery and, characteristically, hyperplasia (formation of new muscle fibers). Its extended half-life keeps the IGF-1 signal active longer than natural IGF-1.
Mechanism of action
It binds the IGF-1 receptor in muscle, activating cell-growth pathways (PI3K/Akt/mTOR). By resisting binding proteins, it stays active longer. It also affects glucose, hence the risk of hypoglycemia.
Quick start guide
Dosing protocol
| Phase | Dose | Frequency | Duration |
|---|---|---|---|
| Standard | 20–50 mcg | 1 time/day (SC) | 4–6 weeks |
Subcutaneous route. Start at the low dose to assess glucose tolerance. The specific dose must be assessed by a healthcare professional.
Reconstitution: units in the syringe
Example with a 1 mg vial + 2 ml of bacteriostatic water → a 0.5 mg/ml solution. On a U-100 insulin syringe (100 units = 1 ml):
| Dose | Volume | Units (U-100) |
|---|---|---|
| 20 mcg | 0.04 ml | 4 U |
| 40 mcg | 0.08 ml | 8 U |
| 50 mcg | 0.10 ml | 10 U |
Is your vial or water different? Calculate the exact units below.
🧮 Calculate your exact syringe dose →⚠️ Who should NOT use it
- People with active cancer — raising GH/IGF-1 is discouraged.
- People with diabetes or a tendency to hypoglycemia (IGF-1 lowers glucose).
- Pregnancy or breastfeeding.
- Always under the supervision of a healthcare professional.
What to expect
- Week 1: greater muscle pump and a sense of recovery.
- Week 1-2: better recovery between workouts.
- Week 2-4: increased lean mass and strength.
- Week 4-6: peak benefits of the cycle.
- Side effects: hypoglycemia, swelling or digestive discomfort.
- Most effective for: muscle growth and intense recovery.
Side effects & safety
- Hypoglycemia: dizziness, sweating or tremor, especially fasted.
- Fluid retention and swelling.
- Digestive discomfort.
- Theoretical concern: IGF-1 is mitogenic (caution in cancer).
- Pain or numbness in the hands.
- Allergic reaction: rash, itching or swelling.
- Symptoms of severe hypoglycemia (confusion, fainting).
- Significant swelling or difficulty breathing.
- Any new, suspicious lump or growth.
- If you are pregnant or planning a pregnancy.
Frequently asked questions
What is IGF-1 LR3?
It is a long-acting analog of insulin-like growth factor 1 that directly stimulates muscle growth.
How does IGF-1 LR3 work?
It binds the IGF-1 receptor and activates cell-growth pathways; its LR3 modification extends its half-life.
What is the usual dose?
Most commonly 20-50 mcg once a day subcutaneously. The regimen must be assessed by a professional.
How does it differ from GH secretagogues?
Secretagogues (CJC-1295, MK-677) raise GH; IGF-1 LR3 directly delivers the final IGF-1 signal.
What are the side effects?
The most important is hypoglycemia; also swelling and digestive discomfort.
Is IGF-1 LR3 approved?
No; it is a research compound not approved by the FDA.
Research areas
- Muscle growth
- Muscle hyperplasia
- Recovery
- Strength
- Anabolism
Related peptides
- MK-677 — Oral secretagogue that raises GH and IGF-1.
- CJC-1295 — GHRH analog of the GH axis.
- Ipamorelin — Selective GHRP; combined with CJC-1295.
Related articles
Related topics
- IGF-1 LR3 for muscle mass
- IGF-1 LR3 dose
- IGF-1 LR3 and hyperplasia
- IGF-1 LR3 and GH
- IGF-1 LR3 side effects
- IGF-1 LR3 cycle
Summary
What it is: Long-acting IGF-1 analog.
How it is researched: Subcutaneous, 20-50 mcg once a day.
Key features: Potent anabolic; hypoglycemia risk. Not FDA-approved.
Related peptides: MK-677, CJC-1295 and Ipamorelin.
References
- Khamsi F et al. (1997). Interactions between follicle-stimulating hormone and growth factors in regulation of deoxyribonucleic acid synthesis in bovine granulosa cells. Biol Reprod. PubMed · DOI
- Khamsi F et al. (2001). Differential effects of insulin-like growth factor-I and gonadotropins on the proliferative activity of two subgroups of granulosa cells: cumulus oophorus and mural granulosa cells. Fertil Steril. PubMed · DOI
Studies compiled from PubMed for informational purposes; many are preclinical or research-stage and do not constitute medical advice.