Performance & GH axis
IGF-1 LR3
Insulin-like Growth Factor 1 Long R3
A modified version of IGF-1 with a much longer active life in the body. IGF-1 is the main hormone through which growth hormone exerts its muscle-building and recovery effects.
Also known as: IGF-1 Long R3, Long R3 IGF-1
- Status
- IGF-1 LR3 is a research compound and not approved by the FDA for human use.
- Evidence
- Early human data. Only small or early-phase studies in people so far.
- Half-life
- ~20-30 hours
- How it's taken
- Subcutaneous or intramuscular injection
- Mechanism
- Anabolic (IGF-1 / myostatin)
- Pathways
- IGF-1, GH axis
How IGF-1 LR3 works
Unlike natural IGF-1 which binds to proteins and gets deactivated quickly, the LR3 modification prevents this binding. This allows it to circulate freely and stimulate muscle cell growth (hyperplasia — creating new muscle cells, not just enlarging existing ones).
What research has looked at
- Promotes muscle cell hyperplasia (new cells)
- Enhanced recovery and repair
- Improved nutrient partitioning
- Extended activity vs. regular IGF-1
Evidence level: Early human data. Only small or early-phase studies in people so far. These are areas studied or reported, not promised effects.
Reported side effects and risks
- Hypoglycemia (low blood sugar)
- Joint pain and swelling
- Organ growth concerns with long-term use
- Gut growth (GI distension)
- Not FDA-approved — significant safety concerns
Sources
- PubMed research on IGF-1 LR3 insulin-like growth factor · NIH · National Library of Medicine
- StatPearls / NCBI Bookshelf on insulin-like growth factor 1 · NCBI Bookshelf
- DrugBank record for mecasermin IGF-1 · DrugBank
Track IGF-1 LR3 in Peptide Vault
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Related compounds
IGF-1 LR3 FAQ
What is IGF-1 LR3?
A modified version of IGF-1 with a much longer active life in the body. IGF-1 is the main hormone through which growth hormone exerts its muscle-building and recovery effects.
How does IGF-1 LR3 work?
Unlike natural IGF-1 which binds to proteins and gets deactivated quickly, the LR3 modification prevents this binding. This allows it to circulate freely and stimulate muscle cell growth (hyperplasia — creating new muscle cells, not just enlarging existing ones).
Is IGF-1 LR3 FDA approved?
No. IGF-1 LR3 is a research compound and not approved by the FDA for human use. Evidence level: early human data. Only small or early-phase studies in people so far.
What is the half-life of IGF-1 LR3?
Reported half-life: ~20-30 hours.
How is IGF-1 LR3 taken?
Subcutaneous or intramuscular injection.
What side effects have been reported with IGF-1 LR3?
Reported in the sources: Hypoglycemia (low blood sugar); Joint pain and swelling; Organ growth concerns with long-term use; Gut growth (GI distension); Not FDA-approved — significant safety concerns.
Educational summary compiled from the sources listed above. Not medical advice. Peptide Vault does not sell, source or recommend any compound. Talk to a qualified clinician before starting or changing anything.