IGF-1 LR3
IGF-1 LR3 (Long R3 insulin-like growth factor-1)
What is IGF-1 LR3?
IGF-1 LR3: Engineered long-acting analogue of insulin-like growth factor-1 with reduced binding to IGF-binding proteins, making it more potent in cell/animal studies. The sources cited here most often discuss it for: Muscle growth, no human data; Growth in catabolic rats; Native IGF-1 is an approved drug. Evidence label: Preclinical.
- Type
- Peptide
- Family
- Growth Hormone Axis
- Evidence label
- Preclinical (2 of 5)
- Regulatory status
- Not FDA-approved for human use and sold as a research chemical; the World Anti-Doping Agency bans IGF-1 variants in competitive sport.
- Goals discussed
- Muscle & Tone, Hormones & Fertility
- Also called
- Long R3 Insulin-like Growth Factor-1, insulin-like growth factor-1, long [Arg3], IGF-1LR3, LR3, igflr3, Long R3 IGF-1
- Last reviewed
- 2026-10-11
- Engineered long-acting analogue of insulin-like growth factor-1 with reduced binding to IGF-binding proteins, making it more potent in cell/animal studies; not approved for human use (the approved IGF-1 drug is mecasermin/Increlex); prohibited in sport.12
Regulatory status Not FDA-approved for human use and sold as a research chemical; the World Anti-Doping Agency bans IGF-1 variants in competitive sport. 3
Names as used in gyms, forums and gray-market listings. Reported, not endorsed; stacks have not been studied as combinations.
At the opposite end, CJC-1295 without DAC, PEG-MGF, and IGF-1 LR3 (tier D) have no peer-reviewed human studies and are supported only by preclinical extrapolation and grey-literature user narratives.
Narrative review grading the evidence for growth hormone and IGF-1 axis peptides from tier A (approved, RCT-backed) to tier D.
What is IGF-1 LR3 researched for?
The three outcomes most discussed for IGF-1 LR3 in the sources below, as those sources report them. humanpeptides.fyi makes no claims of its own: a listed benefit can be unproven or can have failed in trials, and the label on each line says which.
Native IGF-1 is an approved drug
- Native IGF-1 (mecasermin) is FDA-approved for severe primary IGF-1 deficiency in children - shows IGF-1's growth-promoting effects but does not validate LR3FDA label8
What do researchers and users say about IGF-1 LR3?
This underscores that anabolic signalling and body recomposition do not necessarily translate into clinically meaningful physical performance gains
Comment on trials of native IGF-1 in patients with neuromuscular disorders, where lean mass rose without clear functional gains.
Lr3 is a serious gym pump after about 2 weeks but those gains aren't permanent.
Self-report from a long-term user in a forum thread; uncontrolled anecdote.
What side effects of IGF-1 LR3 are reported?
- Hypoglycemia (shakiness, sweating, tunnel vision), especially fastedanecdotal + mecasermin label warns of severe hypoglycemia58
- Possible tumor growthanimal; mecasermin contraindicated with malignancy91
- Unregulated product quality10
- Acromegaly-like changes (enlarged jaw, hands, feet or internal organs) and concern about heart enlargement with prolonged high IGF-1 exposure.theoretical (community guide)3
- Joint pain, water retention, headaches and nausea.anecdotal (community guide)3
- Possible suppression of the body's own growth hormone and IGF-1 production, and receptor desensitization with prolonged use.theoretical (community guide)3
- Feeling drained or lethargic, which users attribute to drops in blood sugar, and warnings that very high IGF-1 can quickly enlarge the waist.anecdotal4
- Raised resting heart rate reported by some users.anecdotal5
What do peptide guides say about IGF-1 LR3?
- PepEdHub PepEdHub describes IGF-1 LR3 as IGF-1 with an arginine swap at position 3 plus a 13-amino-acid extension, which it says reduces binding-protein capture and stretches half-life to roughly a day. 11
- Seek Peptides Seek Peptides calls low blood sugar the most common and immediately dangerous effect, and warns of acromegaly-like enlargement of jaw, hands, feet and organs with prolonged high exposure. 3
- Frontiers in Endocrinology A 2026 review notes off-label reports center on low-blood-sugar symptoms and treats cancer risk as theoretical but clinically relevant, given links between high circulating IGF-1 and several cancers. 2
What does the research say, system by system?
Body & tissues1
- Theoretical organ/tissue overgrowth with IGF-axis stimulation1
Hormones & physiology1
Cells & mitochondria1
- Reduced IGFBP binding gives greater cellular activity in culturein vitro1
Weight & metabolism1
- No human data found; glucose-lowering effect10
Muscle1
- No human data; anecdotal pumps/fullness and recovery4
Also notable1
- Review of GH-IGF1 performance peptides highlights gap between clinical evidence and self-administration2
How strong is the evidence for IGF-1 LR3?
In vitro + inconsistent animal data + anecdotal; no human trials
Mostly cell and animal studies. Human effects unknown. How tiers work
Questions about IGF-1 LR3
What is IGF-1 LR3?
Engineered long-acting analogue of insulin-like growth factor-1 with reduced binding to IGF-binding proteins, making it more potent in cell/animal studies.
Is IGF-1 LR3 FDA-approved?
Not FDA-approved for human use and sold as a research chemical; the World Anti-Doping Agency bans IGF-1 variants in competitive sport.
What is IGF-1 LR3 researched for?
The sources cited on this page most often discuss three outcomes: Muscle growth, no human data; Growth in catabolic rats; Native IGF-1 is an approved drug. Each line above shows what the source reports and how strong that evidence is.
What side effects of IGF-1 LR3 are reported?
Reported in the cited sources: Hypoglycemia (shakiness, sweating, tunnel vision), especially fasted; Possible tumor growth; Unregulated product quality. The list is not complete, and few listed risks does not mean a compound is safe.
How strong is the evidence for IGF-1 LR3?
Evidence label: Preclinical. In vitro + inconsistent animal data + anecdotal; no human trials.
What else is IGF-1 LR3 called?
Names used for it include Long R3 Insulin-like Growth Factor-1, insulin-like growth factor-1, long [Arg3], IGF-1LR3, LR3, igflr3, Long R3 IGF-1.
Does humanpeptides.fyi recommend IGF-1 LR3?
No. humanpeptides.fyi makes no claims and no recommendations of its own. It summarizes and links to what others have published and posted. Nothing here is medical advice; talk to a licensed clinician.