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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.

Doses studied in research

No established dose range

What published trials tested or FDA-approved labels specify. Reporting research facts — not a SmartPeptide recommendation.

No FDA-approved or established trial dose range for this peptide. Anecdotal ranges discussed in community forums exist but are not supported by published clinical trials, and SmartPeptide will not publish unverified doses.

This is the honest answer for peptides like BPC-157, IGF-1 LR3, MOTS-c, Epitalon and similar research compounds — robust human dose- ranging studies have not been published. Always work with a licensed clinician familiar with experimental peptides if you are considering any use.

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
109
total
Human studies
33
MeSH: humans
Clinical trials
1
published
Active trials
0
0 total registered

Recent PubMed studies

Search "IGF-1 LR3 OR long R3 IGF-1" on PubMed

Europe PMC — 2,475 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
3,516
all years
Last 5 years
1,330
recent activity
Open access
3,386
freely readable
OA share
96%
of all works

Human clinical evidence

Semantic Scholar · AI TLDRs · influence-ranked
Total indexed
67
all human + lab studies
Meta-analyses
0
highest evidence
Systematic reviews
1
quality-weighted
Clinical trials
0
published RCTs etc.

Most influential human studies

Ranking blends meta-analysis > systematic review > clinical trial weight with influential-citation count and recency. AI TLDRs by Semantic Scholar / Allen Institute for AI.

Research funding & verification

NIH RePORTER · CrossRef DOI registry

Publication landscape

CrossRef · DOI registry
Indexed works (CrossRef)
1,213,538
all DOIs registered
Retracted papers
0
no retractions on record
Top funders of indexed research
  • National Natural Science Foundation of China60,398 works
  • National Key Research and Development Program of China8,725 works
  • National Institutes of Health6,241 works
  • National Science Foundation6,076 works
  • Fundamental Research Funds for the Central Universities5,850 works
  • China Postdoctoral Science Foundation3,766 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 17 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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