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MuscleAnimal / preclinical only

IGF-1 LR3

Insulin-like Growth Factor 1, Long R3 variant — an analog of human IGF-1 with extended half-life (~20-30 hours vs. ~12 minutes for native IGF-1). Used in research; widely (and controversially) discussed in performance-enhancement communities. NOT FDA-approved for human use; the only approved IGF-1 product is mecasermin (native sequence).

Educational only — not medical advice. SmartPeptide does not prescribe, diagnose, or treat. Always consult a licensed healthcare provider before using any peptide, supplement, medication, or protocol.

What the research shows

Preclinical and ex-vivo work demonstrates IGF-1 LR3 binds IGF-1 receptor with high affinity and produces anabolic signaling. No FDA-approved indication. Mecasermin (recombinant native IGF-1, brand: Increlex) is approved for severe primary IGF-1 deficiency in children — IGF-1 LR3 is NOT the same product.

What's still experimental

Virtually all human use is experimental. Optimal dosing, route, cycling, hypoglycemia management, and long-term cancer risk are all open.

Anecdotal / community reports

Heavy bodybuilding-community use with claims of muscle growth + recovery. Anecdotal reports of severe hypoglycemia events from improper dosing exist. Quality of grey-market product is highly variable.

Anecdotal reports are NOT scientific evidence. They reflect personal experience and may not generalize.

FDA approval status

Source: openFDA + DailyMed (NIH/NLM)
No FDA-approved drug label exists for “IGF-1 LR3”. This peptide is not currently approved by the FDA as a finished pharmaceutical product. Any commercial product claiming FDA approval should be treated with suspicion.

FDA enforcement & recalls

Live · openFDA Drug Enforcement API
Total actions
2
recalls + withdrawals
Ongoing
0
not yet completed
Class I (serious)
0
health hazard / death risk
  • Class IITerminated· Voluntary: Firm initiated
    FDA record

    IGF-1-LR3, 3 mg injection, Rx Only, Promise Pharmacy Compounding Specialists 31818 US Hwy 19N, Palm Harbor, FL 34684

    Reason: Lack of sterility assurance.

    Dec 17, 2018·Promise Pharmacy, LLC
  • Class IITerminated· Voluntary: Firm initiated
    FDA record

    IGF-1 LR3, 620 mcg injection, Rx Only, Promise Pharmacy Compounding Specialists 31818 US Hwy 19N, Palm Harbor, FL 34684

    Reason: Lack of sterility assurance.

    Dec 17, 2018·Promise Pharmacy, LLC
FDA classifications: Class I = reasonable probability of serious adverse health consequences or death. Class II = temporary or medically reversible adverse consequences. Class III = unlikely to cause adverse health consequences.

Mechanism & targets

ChEMBL · UniProt · Open Targets

Molecule (ChEMBL)

View on ChEMBL
Known mechanisms of action
  • CHEMBL1957
    agonistInsulin-like growth factor I receptor agonist

Live research

PubMed · ClinicalTrials.gov · Europe PMC · OpenAlex
PubMed papers
108
total
Human studies
0
MeSH: humans
Clinical trials
0
published
Active trials
0
0 total registered

Europe PMC — 2,449 additional records

Includes EU/UK studies and PubMed Central full-text articles. Often surfaces research weeks before PubMed indexes it.

Research volume (OpenAlex topic graph)

Total works
3,432
all years
Last 5 years
1,290
recent activity
Open access
3,319
freely readable
OA share
97%
of all works

Human clinical evidence

Semantic Scholar · AI TLDRs · influence-ranked
Semantic Scholar API is currently rate-limited.

Human-study summaries for “IGF-1 LR3 OR long R3 IGF-1” are available on Semantic Scholar but the shared free-tier API quota is exhausted right now. Try refreshing in a few minutes, or check the PubMed and Europe PMC panels above for the same literature.

Research funding & verification

NIH RePORTER · CrossRef DOI registry

Publication landscape

CrossRef · DOI registry
Indexed works (CrossRef)
1,197,537
all DOIs registered
Retracted papers
0
no retractions on record
Top funders of indexed research
  • National Natural Science Foundation of China58,879 works
  • National Key Research and Development Program of China8,351 works
  • National Institutes of Health6,141 works
  • National Science Foundation5,990 works
  • Fundamental Research Funds for the Central Universities5,680 works
  • China Postdoctoral Science Foundation3,665 works

Funder diversity is a credibility signal. Research concentrated in a single drug company's funding warrants more scrutiny than research funded across NIH, charities, and academic grants.

Preprints — cutting edge

bioRxiv · medRxiv · via Europe PMC

Preprints have NOT been peer-reviewed. They are early research shared by authors before formal validation. Treat findings as preliminary.

Showing 6 of 15 preprints indexed by Europe PMC.

Known risks

Hypoglycemia (potentially severe — IGF-1 signaling lowers blood glucose), tissue overgrowth concerns, theoretical cancer-promotion signal (IGF-1 pathway is implicated in several cancers). Long-term human safety data is essentially absent. Source purity verification is critical and often impossible.

Reported side effects

Hypoglycemia symptoms (sweating, shakiness, hunger), injection-site reactions, jaw pain (anecdotal), joint pain.

FDA adverse event reports (FAERS)

Updated quarterly by FDA
No reports found in the FDA Adverse Event Reporting System for “IGF-1 LR3”. This is normal for research-only peptides that are not marketed as FDA-approved drugs.

What requires medical supervision

Not FDA-approved. Any use should be under a clinician familiar with growth-factor physiology, with glucose monitoring. The IGF-1 / cancer association alone warrants serious caution.

Questions for your clinician

  • How would we monitor for hypoglycemia and IGF-1 levels?
  • What's the cancer-risk discussion you'd want to have first?
  • What's our exit criteria?

Editorially curated references

Discussions about IGF-1 LR3

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