IGF-1 LR3
aka Long R3 IGF-1, LR3
Modified insulin-like growth factor 1
Half-life
20–30 hours (vs ~20 minutes for native IGF-1)
How long it stays active in your body
Dosing
Post-workout near trained muscle; eat carbs within 20–30 min
How often you take a dose
Route
SubQ · IM
How it goes into the body
Status
Research
Sold for lab research — not approved for humans
What it is
How it works
Activates the IGF-1 receptor with 2–3x potency of native IGF-1 due to reduced binding affinity for IGFBPs (binding proteins that normally inactivate it). Drives satellite cell activation, muscle protein synthesis, and hyperplasia in trained muscle.
What the research says
Animal data robust for muscle growth and satellite cell activation. Human RCT data is limited — most evidence is from bodybuilding observational use. Bachmeyer cites a 600,000-person observational study finding no causal IGF-1/cancer link; others remain cautious.
Sources: PubMed: IGF-1 LR3
Common dosing ranges
- Range
- 20–50 mcg per injection site
- Frequency
- Post-workout near trained muscle; eat carbs within 20–30 min
- Duration
- 4–6 week cycles maximum; receptor desensitization is real
Sources: PubMed
Administration
Side effects
Common
- Hypoglycemia if dosed without carbs
- Site soreness
- Joint pain at high doses
Serious / theoretical
- Theoretical cancer risk (IGF-1 permissive for cell replication)
- Avoid in active malignancy or family history
- Acromegalic features at chronic high doses
Sources: PubMed
Notes
JD Denham and Castore consensus: post-workout + carbs within 30 min is non-negotiable. Bachmeyer says cancer-IGF-1 link comes from metabolic dysfunction, not the peptide. Tatem rates it inferior to real GH for serious lifters.