Compounds / IGF-1 LR3
IGF-1 LR3
Also known as: Long R3 IGF-1; LR3-IGF-1; Long Arginine-3 IGF-1; IGF-1 LR3
Primary research focus: Cell-culture and growth-factor research (IGF-1 receptor signaling); not for human use
Last updated July 2026 · Reviewed against FDA labeling and published research.
What is IGF-1 LR3?
IGF-1 LR3 (Long R3 IGF-1) is a synthetic 83-amino-acid analog of human insulin-like growth factor 1 (native IGF-1 is 70 amino acids). It is engineered to bind IGF-binding proteins far more weakly than native IGF-1, which leaves more of it in the free, active state and greatly extends its functional half-life. Its main legitimate use is as a potent cell-culture supplement in biopharmaceutical production; it is not FDA-approved for any human use and is prohibited in sport.
IGF-1 LR3 binds and activates the IGF-1 receptor (IGF-1R), a receptor tyrosine kinase, triggering PI3K/Akt and MAPK/ERK signaling that drives protein synthesis, cell proliferation, glucose uptake, and anti-apoptotic effects. Two structural changes account for its potency: an arginine substituted for glutamate at position 3, and a 13-residue N-terminal extension. Together these reduce IGF-binding-protein affinity roughly a thousandfold while preserving IGF-1R binding, so a much larger free fraction remains available and its half-life is extended from minutes to many hours.
How it’s supplied
Not an FDA-approved or human-use medicine. It is sold as a research-grade lyophilized powder for reconstitution and as a cell-culture reagent. Research-grade material is not FDA-reviewed for potency or sterility, and there is no oral or topical human product.
Dosage Chart
Units shown are for a U-100 insulin syringe (100 units = 1 mL), calculated from the vial size and BAC water you select. Always confirm against your prescription and your syringe markings.
| Phase | Dose | Frequency | Notes |
|---|---|---|---|
| Weeks 1-2 | 20mcg | 1x Daily | — |
| Weeks 3-4 | 40mcg | 1x Daily | — |
| Weeks 5-8 | 50mcg | 1x Daily | — |
- Rotate injection sites to reduce irritation and lipohypertrophy
- Not for use during pregnancy or breastfeeding
- Do not exceed the recommended dose to try to speed results
Potential Benefits and Side Effects
Effects reported in published research. Not a promise of results, and not medical advice.
- Reported in cell-culture and preclinical animal research only; no established human benefits.
- Potent, stable activation of the IGF-1 receptor for cell proliferation and survival in culture.
- Reduced IGF-binding-protein sequestration and greatly extended functional half-life versus native IGF-1.
- Preclinical effects on organ and intestinal growth and protein metabolism in animal models.
- No human adverse-effect data are available.
- Based on IGF-1 biology, plausible concerns include hypoglycemia, tissue overgrowth, and joint or organ effects.
- Sustained IGF-1R activation raises theoretical cancer-promotion concerns.
- Research-grade material carries identity and purity risks.
Warnings and contraindications
Important safety information. This is not exhaustive — read the full prescribing information and consult your prescriber or pharmacist.
- No FDA-approved labeling exists; the following reflect the compound's status and biology, not a drug label.
- There are no human clinical trials of IGF-1 LR3; human safety is not established.
- Sustained, high IGF-1R activation carries theoretical risks including hypoglycemia (insulin-like effects), promotion of existing tumors, and organ or tissue overgrowth.
- It is prohibited in sport under the WADA Prohibited List (S2).
- Research-grade material varies in identity and purity.
- Safety in pregnancy and breastfeeding has not been studied.
- Not established; no FDA labeling. Precautionary considerations include active or suspected malignancy (IGF-1R growth signaling), hypoglycemia risk, and known hypersensitivity.
Reconstitution Steps
How to prepare the lyophilized vial. Confirm specifics with your pharmacist or prescriber.
- Confirm the amount of peptide in the vial and the volume of diluent you intend to use before starting.
- Wash your hands and gather supplies: the lyophilized vial, the diluent (typically bacteriostatic water), an alcohol swab, and a sterile syringe.
- Let the vial and diluent reach room temperature if they were refrigerated or frozen.
- Wipe the rubber stopper of both the peptide vial and the diluent vial with a fresh alcohol swab and let them air dry.
- Draw the intended diluent volume into the syringe.
- Insert the needle into the vial and slowly release the diluent down the inside wall rather than directly onto the powder, to avoid foaming.
- Do not shake. Gently swirl or roll the vial until fully dissolved.
- Inspect the solution: it should be clear and colorless with no visible particles. Do not use if cloudy or containing particles.
- Note the resulting concentration (amount divided by diluent volume) so it matches the reconstitution calculator on this page.
- Label the vial with the reconstitution date and store as directed under reconstituted storage.
US regulatory status
Classifications are public record but can change. For reference only, not legal advice.
Development: IGF-1 LR3 was developed as a laboratory tool: its resistance to IGF-binding proteins makes it a potent, stable growth factor for serum-free and low-serum cell culture, and it is used widely in biopharmaceutical manufacturing (for example, monoclonal-antibody cell lines). Preclinical animal studies have examined effects on organ growth, intestinal growth, and protein metabolism. It has never been developed as a human therapeutic and has no clinical trials; the FDA-approved IGF-1 product for humans is mecasermin (Increlex), which is native recombinant IGF-1, not the LR3 analog. It is prohibited in sport, and validated detection assays exist for anti-doping.
Notes: IGF-1 LR3 is not FDA-approved for any human use and is sold as a research reagent, outside FDA quality oversight. It is not on the FDA 503A bulk drug substances list and is not eligible for 503A or 503B compounding; the compoundable/approved IGF-1 species is mecasermin (native IGF-1), not LR3. IGF-1 and its analogs are prohibited at all times in sport under the WADA Prohibited List (category S2). It is not a controlled substance.
International status
Pharmacokinetics
Storage and handling
Important Notes
Practical considerations for consistency and safety.
- IGF-1 LR3 is a research and cell-culture reagent, not a human medicine; its legitimate use is in the laboratory.
- It is distinct from mecasermin (Increlex), the FDA-approved native IGF-1 for severe primary IGF-1 deficiency.
- Its extended half-life means systemic exposure is far greater than native IGF-1, amplifying both effects and risks.
- It is banned in sport (WADA S2) with validated detection assays.
- There are no human trials or human safety data.
Lifestyle Factors
- Its legitimate use is in laboratory cell culture, not human administration.
- Human lifestyle interactions are not characterized.
References
Related compounds
Important disclaimer
This page is an educational reference, not medical advice, a diagnosis, or a treatment recommendation, and not a substitute for your prescriber or pharmacist. Approval and regulatory status varies by compound and can change. Always confirm against current prescribing information and consult a qualified healthcare professional before making any decision about a medication.