IGF-1 LR3
Modified Growth Factor Analog · Muscle Growth
IGF-1 LR3 is a synthetic 83-amino acid analog of insulin-like growth factor-1 that has never been approved for human use. The N-terminal extension and R3 substitution reduce binding protein interaction, maintaining elevated free circulating levels with ~3x greater potency than native IGF-1.
Overview
IGF-1 LR3 is a synthetic 83-amino acid analog of insulin-like growth factor-1 that has never been approved for human use. The N-terminal extension and R3 substitution reduce binding protein interaction, maintaining elevated free circulating levels with ~3x greater potency than native IGF-1.
Functions as a full IGF-1 receptor agonist activating PI3K/Akt/mTOR and MAPK/ERK pathways. The modifications prevent protein sequestration, maintaining elevated free circulating levels for extended anabolic effects.
Research indications
What the compound has been studied for, grouped by body system. Effect size is the reported magnitude where it was measured — not a recommendation.
15-20% lean mass gains in 4 weeks through satellite cell activation (rat studies).
Cancer cachexia rats maintained 30% more muscle versus placebo.
Creates new muscle fibers via satellite cell differentiation.
Accelerated wound healing in animal models.
Enhanced connective tissue repair.
Directs nutrients toward muscle tissue.
Enhanced lipolysis through IGF-1 pathway.
A large effect in a weak study and a small effect in a strong one are different things. Effect size is never evidence of use in people.
- Class
- Synthetic IGF-1 analog
- Chain length
- 83 residues
- Half-life
- ~25 h
- Typical dose
- 20-100 mcg daily (start low at 20-30 mcg)
- Frequency
- Once daily, or split AM/PM for higher doses
- Cycle length
- 4-6 weeks maximum
- Storage
- Lyophilized: -20°C to -80°C. Reconstituted in acetic acid: 2-8°C for 1 year. Reconstituted in BAC water: use within 7 days
Molecular data
- Type
- Synthetic IGF-1 analog
- Chain length
- 83 residues
- Half-life
- 1500 min
Dosing reference
Doses reported in the literature and by suppliers. These are a record of what has been used in research — reference, never instruction.
| Context | Route | Amount | Frequency |
|---|---|---|---|
| Beginner Protocol | SubQ/IM | 20-30mcg | Once daily post-workout |
| Intermediate | SubQ/IM | 40-60mcg | Once daily |
| Advanced | SubQ/IM | 80-100mcg | Once or split AM/PM |
| Women's Protocol | SubQ/IM | 10-20mcg | Once daily |
Interactions
Creates excessive IGF-1 levels; avoid combination.
Both stimulate GH/IGF-1 axis; use caution with combination.
May compound metabolic effects through GH stimulation.
Synergistic hypoglycemic effects can be life-threatening.
Complementary healing mechanisms.
Different repair pathway activation.
Amplified effects with increased risks.
May mitigate insulin resistance.
Additive neurotrophic pathway effects.
Quality checklist
- ✓HPLC purity >95%
- ✓Mass spectrometry confirmation
- ✓Cold storage maintained (-20°C lyophilized)
- ✓Certificate of analysis from reputable source
- !Research chemical status - never approved for human use
- !Zero human clinical trials exist
- !Species-specific responses vary significantly
- ×Severe hypoglycemia risk - life-threatening low blood sugar lasting 20-30 hours
- ×Cancer proliferation concern - UK Biobank links elevated IGF-1 to multiple cancers
- ×Black market quality varies - oxidized and degraded forms common
What to expect
Safety
- Hypoglycemia (lasting up to 30 hours) - CRITICAL
- Water retention
- Joint stiffness
- Muscle soreness
- Increased pump during workouts
- Severe or recurring hypoglycemia despite carbohydrate intake
- Unusual growths, lumps, or rapid mole changes
- Severe joint pain or carpal tunnel symptoms
- Persistent nausea, headaches, or vision changes
- Signs of organ enlargement
- Extreme fatigue or mental fog
- NEVER approved for human use - research chemical only
- Cancer history or undiagnosed growths
- May cause organ hypertrophy (heart, intestines)
- WADA prohibited - causes failed drug tests
FAQ
Why is IGF-1 LR3 called 'long R3'?
The N-terminal extension and R3 (arginine) substitution reduce binding to IGF binding proteins, allowing the peptide to circulate freely for 20-30 hours instead of being sequestered. This gives it approximately 3x greater potency and systemic presence than native IGF-1.
Can I take IGF-1 LR3 with HGH?
Not recommended. Both are IGF-1 pathway agonists, and combining them creates excessive IGF-1 levels with amplified side effects including severe hypoglycemia, joint pain, organ enlargement risk, and carpal tunnel symptoms.
How long can I safely use IGF-1 LR3?
Maximum recommended cycle is 4-6 weeks with equal off-time. Prolonged use risks receptor desensitization, excessive organ growth, and cumulative hypoglycemia danger. Most users run 4-6 week cycles with 4-6 weeks off between.
What happens if my blood sugar drops dangerously low on IGF-1 LR3?
Severe hypoglycemia from IGF-1 LR3 can last 20-30 hours due to the long half-life. Consume 30-60g fast carbs immediately after injection and keep glucose tablets handy. Never inject before sleep. Consider having glucagon available for emergency hypoglycemia.
References
- 1Insulin-like growth factor-I (IGF-I) and especially IGF-I variants are anabolic in dexamethasone-treated ratsTomas FM, Knowles SE, Owens PC, Chandler CS, Francis GL, Read LC, Ballard FJ · Biochemical Journal · 1992
Des(1-3) IGF-1 and LR3-IGF-1 were significantly more potent than native IGF-1 in reversing dexamethasone-induced muscle wasting in rats, with truncated and modified variants showing superior anabolic activity.
animalPubMed 1371669 ↗ - 2Insulin-like growth factor I preserves host lean tissue mass in cancer cachexiaNg EH, Rock CS, Lazarus DD, Stiaino-Coico L, Moldawer LL, Bhatt GR · American Journal of Physiology · 1992
IGF-1 treatment effectively attenuated host muscle protein and lean tissue depletion in a sarcoma model without stimulating tumor growth. Dose-dependent increases in carcass weight and gastrocnemius muscle protein.
reviewPubMed 1373040 ↗ - 3Circulating Insulin-like Growth Factor-I Concentrations and Risk of 30 Cancers: Prospective Analyses in UK BiobankMurphy N, Knuppel A, Papadimitriou N, Martin RM, Tsilidis KK, Brennan P et al. · Cancer Research · 2020
Higher circulating IGF-1 associated with increased risks of colorectal, breast, prostate, and thyroid cancers in >395,000 UK Biobank participants, underscoring the cancer risk of sustained IGF-1 pathway activation.
reviewPubMed 32709735 ↗ - 4Attenuated glucose-stimulated insulin secretion during an acute IGF-1 LR3 infusion into fetal sheep does not persist in isolated isletsStremming J, White A, Galan HL, Brown LD · American Journal of Physiology - Regulatory, Integrative and Comparative Physiology · 2023
Fetal plasma insulin concentrations decreased 66% with IGF-1 LR3 infusion during hyperglycemic clamp. Insulin secretion suppression was acute and did not persist in isolated islets.
reviewPubMed 37114757 ↗