Library / Peptides / Metabolic & Body Composition / IGF-1 LR3
Emerging evidence · Grade B

IGF-1 LR3

IGF-1 LR3 (Long Arginine 3 Insulin-like Growth Factor-1)
Evidence
Emerging
Route
Subcutaneous or intramuscular injection
Frequency
Once daily (often post-workout)
Category
Metabolic & Body Composition
TL;DR
IGF-1 LR3 is a synthetic, modified version of insulin-like growth factor-1 (IGF-1). The modification — substitution of arginine at position 3 and extension of the N-terminal by 13 amino acids — reduces its binding to IGF-binding proteins, resulting in a significantly longer half-life and greater bioavailability than native IGF-1.
Part 01 · How it works

Mechanism.

IGF-1 LR3 is a synthetic, modified version of insulin-like growth factor-1 (IGF-1). The modification — substitution of arginine at position 3 and extension of the N-terminal by 13 amino acids — reduces its binding to IGF-binding proteins, resulting in a significantly longer half-life and greater bioavailability than native IGF-1. It is a potent anabolic peptide used primarily in research settings and off-label for muscle growth and recovery.

Native IGF-1 is like a delivery driver who keeps getting stopped at checkpoints (binding proteins) before reaching the destination. IGF-1 LR3 is the same driver with a VIP pass that lets it bypass most checkpoints, so more of the growth signal actually reaches the muscles.

Mechanism · technical
IGF-1 LR3 binds to the IGF-1 receptor (IGF-1R), activating the PI3K/Akt and MAPK/ERK signaling cascades. This promotes protein synthesis, cell proliferation, and inhibits apoptosis in muscle and other tissues. Because it has reduced affinity for IGF-binding proteins (IGFBPs), more of the peptide remains free and active in circulation compared to native IGF-1, giving it approximately 2-3 times the potency. It promotes both muscle hypertrophy and hyperplasia (increasing cell number, not just cell size).
Part 02 · Dosing & administration

How it's taken.

Community-reported · unregulated

Values below reflect commonly reported community protocols for IGF-1 LR3. These are anecdotal and unregulated — not clinically validated and not a recommendation. Provided for educational purposes only — this is not medical advice and not instructions for self-administration. Consult your healthcare provider before making any health decision.

Standard dose
20-50 mcg/day
Subcutaneous or intramuscular injection · Once daily (often post-workout)
Duration
10 days on, 4 weeks off (community-standard cycle)
·
The most-documented protocol is 10 days on / 4 weeks off to limit IGF-1 receptor desensitization; a continuous 4–6 week run is less common and higher risk.
·
No human clinical dosing data exist — figures are entirely community/bodybuilding; potent IGF-1 receptor agonism carries a real hypoglycemia risk requiring blood-glucose caution.
·
Research compound of unverified quality, not FDA-approved, and WADA-prohibited.
Need help with reconstitution?

Use the free peptide calculator for dilution, unit conversion, and injection volume.

Open calculator
Part 03 · Safety

Side effects, rare serious events, who shouldn't.

Reported side effects
Hypoglycemia is the primary acute risk, as IGF-1 has insulin-like effects on glucose uptake. Other side effects include joint pain, jaw pain, edema, headache, and potential for organ enlargement (acromegaly-like effects) with chronic use. There is theoretical concern about promoting growth of pre-existing tumors, as IGF-1 signaling is implicated in cancer cell proliferation.
Absolute · do not use
×
Active malignancy or history of cancer (IGF-1 is a potent growth factor for tumor cells)
×
Diabetic retinopathy
×
Pregnancy or breastfeeding
×
Children under 18
×
Known hypersensitivity to IGF-1 LR3 or any component
×
Pituitary tumor
Interactions
Insulin
IGF-1 has insulin-like activity; significant risk of hypoglycemia when combined
Major
Oral hypoglycemics (sulfonylureas, metformin)
Additive glucose-lowering effect; close blood glucose monitoring required
Major
Growth hormone therapy
GH stimulates endogenous IGF-1; exogenous IGF-1 LR3 adds to total IGF-1 activity with increased risk of side effects
Moderate
Anticoagulants
IGF-1 may affect platelet function; monitor coagulation parameters
Minor
Labs to monitor
IGF-1
Baseline and every 2 weeks during use
Monitor for supraphysiologic IGF-1 levels
Fasting Glucose & Insulin
Baseline and weekly initially
IGF-1 has insulin-like effects and can cause hypoglycemia
CMP (Comprehensive Metabolic Panel)
Baseline and every 3 months
Liver and kidney function
HbA1c
Baseline and at end of cycle
Track glycemic effects over time
CBC with Differential
Baseline and monthly
Monitor for potential hematologic effects
Part 04 · Research log

Every study we cite.

Each study with its published finding and a plain-language note on limitations or funding.

01
2002
0
IGF-1 LR3 structure and binding properties
LR3 variant has reduced IGFBP binding, resulting in enhanced bioavailability and potency compared to native IGF-1
Biochemical characterization study
02
2002
0
IGF-1 and skeletal muscle hypertrophy
IGF-1 signaling is critical for muscle hypertrophy via PI3K/Akt/mTOR pathway activation
Well-established mechanism; multiple corroborating studies
PMID 12163223 ↗
Part 05 · Cost & access

Where you can get it.

Regulatory status
IGF-1 LR3 is not FDA-approved. Mecasermin (Increlex), which is recombinant native IGF-1, is FDA-approved for severe IGF-1 deficiency. IGF-1 LR3 is sold as a research chemical and is prohibited by WADA. It is not available through standard compounding pharmacies.
The Peptide Column takes no affiliate commission from any source.
Part 06 · Your appointment

Questions to bring.

01
What are the risks of exogenous IGF-1 use regarding cancer promotion?
02
How should I monitor my blood glucose while using IGF-1 LR3?
03
What baseline labs (IGF-1, fasting glucose, insulin, HbA1c) should I have?
04
Is there a risk of organ growth or cardiac hypertrophy with IGF-1 LR3?
05
How does IGF-1 LR3 differ structurally and pharmacokinetically from FDA-approved mecasermin?
06
What is the safest protocol for IGF-1 LR3 use?
References

Every citation, numbered.

Citation list. For our editorial read of each study — including bias flags and quality grades — see the Research log above.

  1. 01.
    IGF-1 LR3 structure and binding properties · 2002
  2. 02.
    IGF-1 and skeletal muscle hypertrophy · 2002 · PMID 12163223 ↗