IGF-1 LR3
Also known as: Long R3 IGF-1, IGF-1 Long Arg3
By GLPeptideSciences Editorial Team · How we evaluate evidence · Reviewed by Dr. George S. Watson, MD, Cardiothoracic Surgeon · Updated 2026-06-02
A modified, long-acting analog of insulin-like growth factor 1 used as a research chemical for its anabolic signaling — with meaningful safety concerns.
What it is & how it works
What it is
IGF-1 LR3 (“Long R3”) is a modified, long-acting version of IGF-1 — the growth factor through which much of growth hormone’s anabolic effect is actually mediated. Unlike secretagogues, it supplies the signal directly.
How it is thought to work
The modifications extend its half-life and reduce binding to carrier proteins, so it produces a stronger, more sustained IGF-1 effect than native IGF-1.
The evidence and the caveat
This is where caution matters most. Driving IGF-1 directly can cause hypoglycemia and undesired tissue growth, and sustained high IGF-1 signaling carries well-documented long-term risk concerns. It’s a research reagent, not a validated human therapeutic.
What it's discussed & studied for
- Muscle growth and anabolic signaling (research-market)
- Recovery discussion (anecdotal)
Discussion of a use is not a claim that it works or is approved.
Research status
A research reagent rather than an approved therapeutic. Human use is off-label/unapproved and the risk profile is taken seriously in the literature on IGF-1 signaling.
Evidence quality
IGF-1 biology is well understood; evidence that injecting LR3 safely produces the desired body-composition outcomes in humans is weak, and the risks are real.
Dosing discussion
No approved or validated human protocol. Because it directly drives IGF-1 signaling, dosing errors carry real consequences (including hypoglycemia).
Educational summary of what is discussed in the literature and community — not a dosing recommendation or medical advice.
Safety & harm reduction
Notable concerns: hypoglycemia, undesired tissue growth, and the long-standing caution that sustained high IGF-1 signaling is associated with adverse long-term risks. This is not a casual compound.
Sourcing literacy
No approved product; research-market material is unverified, and potency variability raises the stakes given the hypoglycemia risk.
Selected literature
FAQ
Why is IGF-1 LR3 considered higher-risk?
It directly drives IGF-1 signaling rather than nudging the body's own output, so it can cause hypoglycemia and undesired tissue growth, and sustained high IGF-1 carries long-term risk concerns.