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Growth factor researchNot approved (US)

IGF-1 LR3

Long R3 IGF-1 · Long R3 Insulin-like Growth Factor-1

LR3 fully activates IGF1R. Its reduced binding to IGFBPs leaves a larger free, biologically available fraction. Downstream PI3K/Akt/mTOR signaling promotes protein production and proliferation, alongside increased glucose uptake and activation of satellite cells.

Not medical advice. Educational reference only.

Typical dose
20 mcg initially, 40–80 mcg standard, 80–120 mcg advanced short-cycle: subcutaneous once daily
Route
Subcutaneous injection
Cycle
Short cycles; no numeric duration established; include washout periods to limit receptor desensitization
Storage
Keep at 2–8°C after mixing and use within 28 days.

What is IGF-1 LR3?

IGF-1 LR3 is a recombinant version of insulin-like growth factor-1. An Arg3 replacement and an extension of 13 amino acids at the N-terminus greatly weaken binding to IGF-binding proteins. These changes increase tissue exposure and anabolic activity, with an approximate half-life of 20–30 hours compared with 12–15 hours for native IGF-1. It remains an experimental compound without FDA approval.

Mechanism of action

LR3 fully activates IGF1R. Its reduced binding to IGFBPs leaves a larger free, biologically available fraction. Downstream PI3K/Akt/mTOR signaling promotes protein production and proliferation, alongside increased glucose uptake and activation of satellite cells.

Targets: IGF-1 receptor (IGF1R) · PI3K/Akt/mTOR pathway

Research indications

  • Growth Hormone Support

    Most effective

    Pituitary signaling is linked to increased release of endogenous growth hormone.

  • Body Composition

    Effective

    Potential changes include more lean tissue and a lower proportion of body fat.

  • Recovery & Repair

    Effective

    Investigations address tissue restoration and recovery following injury or exercise.

  • Sleep Quality

    Moderate

    Some experimental schedules are associated with deeper slow-wave sleep and more restorative rest.

Research protocols

These are commonly discussed research protocols — not medical advice. Consult a healthcare provider before use.

GoalAmountFrequencyRoute
Conservative Start (Week 1-2)20 mcgOnce dailySubcutaneous injection
Standard Body Comp Range40–80 mcgOnce dailySubcutaneous injection
Advanced Short Cycle80–120 mcgOnce dailySubcutaneous injection

Interactions

  • Insulin / IGF-1

    Monitor

  • Corticosteroids

    Caution

  • Thyroid Hormones

    Monitor

  • BPC-157

    Compatible

  • TB-500

    Compatible

  • Ipamorelin + CJC-1295

    Compatible

    The combination aims for synergistic GH responses; this compatibility category does not establish interaction safety.

  • Somatostatin Analogs

    Avoid

How to reconstitute and inject

Diluent: Use bacteriostatic water only; avoid saline because precipitation can occur.

  1. Let the refrigerated vial warm to room temperature for 15–20 minutes before preparing it.
  2. Disinfect the stopper using an alcohol swab, then wait until the surface has dried fully in the air.
  3. Use a sterile syringe to measure your calculated amount of bacteriostatic water. Use this diluent only; avoid saline because precipitation may occur.
  4. Introduce the water gradually against the inner glass wall. Keep the stream away from the peptide powder itself.
  5. Rotate the vial gently to mix its contents. Do not shake forcefully, because vigorous agitation can degrade the peptide.
  6. Wait 2–3 minutes for the powder to dissolve completely. Check that the liquid is transparent and has no color.
  7. Measure your calculated dose with an insulin syringe in preparation for administration beneath the skin.
  8. Use the abdomen, thigh or upper arm for subcutaneous administration. Change the injection location each time to help prevent lipodystrophy.
  9. Return the mixed vial to refrigeration at 2–8°C. Use the prepared solution within 28 days of mixing.

What to expect

Week 1–2
Sleep may start improving, with mild fluid retention possible during the early period.
Week 2–4
Sleep may deepen and recovery improve; a slight rise in appetite is also possible.
Week 4–8
Changes in energy, the balance of fat and lean tissue, and speed of recovery may become noticeable.
Week 8–12
Visible changes may include better skin quality, less body fat and more lean tissue.
Week 12+
Improvements in strength, body composition and general vitality may persist. These are proposed research timelines rather than established individual outcomes.

Side effects and safety

  • Fluid retention and mild abdominal bloating, particularly at the beginning
  • Greater appetite, particularly with members of the GHRP class
  • Warmth or flushing around the injection location
  • Numbness or tingling, with carpal tunnel-like effects at larger doses
  • Lethargy or tiredness when the timing of administration is unsuitable
  • Possible increases in prolactin and cortisol, especially with GHRP-6
  • Higher blood glucose; monitor levels if you have diabetes or prediabetes · Rare

IGF-1 LR3: not approved in the US.

Regulatory status

  • US

    Not approved

    FDA — experimental use only, without therapeutic approval. The regulatory record indicates no prescription requirement, no 503A ban and no applicable telehealth pathway.

    Rx required
    No
    Telehealth
    N/A

Frequently asked questions

What is IGF-1 LR3?

LR3 has an Arg3 replacement and a 13-residue extension that reduce IGFBP binding and prolong exposure.

How does LR3 compare with HGH?

HGH acts upstream at growth hormone receptors, gradually increasing IGF-1 production. LR3 directly stimulates IGF1R. HGH protocols usually pursue longer endocrine modulation, whereas LR3 discussions more often concern shorter cycles for anabolic or recovery goals.

Which schedules are discussed?

Experimental schedules begin at about 20 mcg daily, then increase toward 40–80 mcg according to tolerance and goals. Higher amounts appear in advanced, shorter cycles. Limits on cycle length and intervening washout periods aim to reduce receptor desensitization; these practices do not establish an approved human regimen.

What monitoring matters?

Monitor blood glucose because altered glucose handling can lead to hypoglycemia. In supervised settings, also assess fluid accumulation, joint discomfort and changes in recovery. These checks address potential adverse effects rather than proving that treatment is safe.

References

  1. Insulin-like growth factor-I and its binding proteins in sport and exercise medicine (2011)

  2. Intranasal long R3 insulin-like growth factor-1 treatment promotes amyloid plaque remodeling in cerebral cortex but fails to preserve cognitive function in male 5XFAD mice. (2025)

    PMID 39610283DOI 10.1177/13872877241299056

  3. Revolutionary decellularized Alstroemeria stem-based nerve conduit integrated with GelMA and controlled IGF-1 LR3 release for enhanced rat sciatic nerve regeneration. (2025)

    PMID 41015370DOI 10.1016/j.ijbiomac.2025.147888

  4. IGF-1 LR3 studies on ClinicalTrials.gov (2024)