Overview
IGF-1 LR3 is a growth hormone-related peptide. Long R3 variant of insulin-like growth factor 1 — 83-amino acid analog with reduced IGF binding protein affinity.
With a half-life of ~20 hours, IGF-1 LR3 requires daily administration in most observed protocols. Administered via SubQ injection, it has a bioavailability of approximately 95% via its primary route.
Half-life approximately 20 hours (vs ~15 minutes for native IGF-1). Subcutaneous administration. One-compartment model.
Mechanism of Action
IGF-1 LR3's pharmacological activity involves the following key pathways:
Growth Factor Signaling
IGF-1 LR3 binds to IGF-1 receptors, activating downstream signaling cascades involved in cell growth and tissue repair.
Dosing Protocols
The following protocols represent commonly observed dosing patterns. These are observational summaries, not recommendations.
Dose
20 mcg/day
Route
Subcutaneous
Frequency
Once daily
Duration
4-12 weeks
Dose
60 mcg/day
Route
Subcutaneous
Frequency
Once daily
Duration
4-12 weeks
Reconstitution Steps
IGF-1 LR3 is supplied as a lyophilized (freeze-dried) powder and requires reconstitution before use. Common vial sizes: 0.1 mg, 1 mg.
-
1
Prepare Your Workspace
Gather the IGF-1 LR3 vial, bacteriostatic water, alcohol swabs, and an insulin syringe. Wipe down the surface and wash hands thoroughly.
-
2
Swab Vial Tops
Clean the rubber stoppers of both the IGF-1 LR3 vial and the bacteriostatic water vial with separate alcohol swabs. Allow to air dry.
-
3
Draw Bacteriostatic Water
Using an insulin syringe, draw the desired volume of bacteriostatic water. For a 1 mg vial, 1 mL yields 1,000 mcg/mL; 2 mL yields 500 mcg/mL.
-
4
Add Water to Peptide Vial
Insert the needle into the IGF-1 LR3 vial and release the water slowly down the inside wall of the vial. Do not inject directly onto the lyophilized powder, as this can damage the peptide.
-
5
Dissolve Gently
Allow the solution to sit for 1–2 minutes, then swirl gently until the powder is fully dissolved. Do not shake vigorously, as agitation can degrade the protein structure.
-
6
Label and Store
Label the vial with the reconstitution date and concentration. Store upright in a refrigerator at 2–8°C. Use within 28 days of reconstitution.
Quick Reconstitution Math
1 mg vial + 1 mL bacteriostatic water = 1,000 mcg/mL. For a 50 mcg dose, draw 5 units (0.05 mL) on a U-100 insulin syringe. Use the Milligram reconstitution calculator for custom vial sizes.
Lyophilized powder is stable for up to 12 months at -20°C. After reconstitution with bacteriostatic water, refrigerate at 2–8°C and use within 28 days. Avoid repeated freeze-thaw cycles.
Frequently Asked Questions
What is IGF-1 LR3 and how does it differ from native IGF-1?
IGF-1 LR3 (Long R3 Insulin-like Growth Factor-1) is a synthetic 83-amino-acid analogue of human IGF-1. It differs from native IGF-1 by an arginine substitution at position 3 and an additional 13-amino-acid extension at the N-terminus. These modifications reduce binding to IGF-binding proteins (IGFBPs), resulting in approximately three times the potency of native IGF-1 and a significantly extended half-life of around 20 hours compared to roughly 15 minutes for unmodified IGF-1.
What is the half-life of IGF-1 LR3 and how does it affect dosing?
IGF-1 LR3 has an effective half-life of approximately 20–30 hours, which is substantially longer than native IGF-1. Following subcutaneous injection, peak plasma concentration is typically reached around 7 hours post-administration. This extended half-life supports once-daily dosing schedules, though some protocols alternate days to allow receptor resensitization between doses.
How does IGF-1 LR3 work at the cellular level?
IGF-1 LR3 binds to the IGF-1 receptor on cell surfaces, activating intracellular signaling cascades – primarily the PI3K/Akt/mTOR pathway. This stimulates protein synthesis, inhibits protein breakdown, and drives cellular growth and differentiation. Because it has minimal affinity for IGFBPs, a greater proportion of the administered dose remains bioavailable in circulation compared to native IGF-1.
How long does IGF-1 LR3 take to produce noticeable effects?
Circulating IGF-1 levels change rapidly after the first dose, but observable physiological effects typically begin to emerge within 1–2 weeks. Body composition and recovery-related changes are more commonly reported after 3–4 weeks of consistent use. Because the compound reaches pharmacokinetic steady state within approximately 4 days, the lag between steady levels and subjective effects reflects the time needed for downstream tissue adaptation.
What is the typical cycle duration for IGF-1 LR3?
IGF-1 LR3 protocols commonly run for 4–6 weeks, with an off-cycle period of equal length to allow IGF-1 receptors to resensitize. Protocols exceeding 8 weeks are uncommon due to concerns about receptor desensitization and diminishing response over time. Shorter cycles with adequate breaks between them are the most widely observed pattern.
What are common side effects observed with IGF-1 LR3?
The most frequently reported side effects include transient hypoglycemia (low blood sugar), water retention, and joint discomfort. Hypoglycemia tends to be dose-dependent and is most pronounced shortly after injection. Headaches and localized injection site reactions are also commonly noted. These effects are generally mild at standard dosage ranges and tend to diminish as the body adapts over the first several days.