Verified July 2026 · Cited to primary sources
IGF-1 LR3: Evidence Grade D — Animal studies only, unproven in humans.
The honest verdict
IGF-1 LR3 is not FDA-approved and not legally compoundable — research-only. Human evidence is Grade D: there is no published human efficacy trial for the analogue itself, so the muscle-growth claims rest on mechanism, not proof. It is also WADA-prohibited (S2). We don't link gray-market sources.
IGF-1 LR3 at a glance
- Class
- Synthetic long-acting analogue of insulin-like growth factor 1 (IGF-1)
- Mechanism
- A modified, long-acting form of IGF-1 that activates the IGF-1 receptor to drive the PI3K/Akt/mTOR protein-synthesis and satellite-cell pathways — the theoretical basis for its muscle-growth marketing.
- Also known as
- Long R3 IGF-1, IGF-1 Long Arg3, LR3-IGF-1
- Research applications
- Muscle growth and body recomposition (marketed; no published human efficacy RCT)
- Research reagent / cell-culture growth supplement (its legitimate laboratory use)
- Forms
- subcutaneous injection
- Legal status
- Research-only
- WADA (anti-doping)
- Prohibited (S2 — IGF-1 and its analogues explicitly named) at all times
- Evidence grade
- Grade DAnimal studies only, unproven in humans
How we grade evidence
Every grade is assigned by a fixed A–F rubric — human-trial strength, not hype or affiliate status. Last verified July 6, 2026.
What is IGF-1 LR3?
A long-acting IGF-1 analogue marketed for muscle growth on the strength of its mechanism alone — there is no published human efficacy trial for it, and it's banned in sport.
A modified, long-acting form of IGF-1 that activates the IGF-1 receptor to drive the PI3K/Akt/mTOR protein-synthesis and satellite-cell pathways — the theoretical basis for its muscle-growth marketing.
How strong is the evidence for IGF-1 LR3?
Grade D: there is no published human efficacy RCT of IGF-1 LR3 itself (rule 5 fired — animal/mechanistic evidence only, no human efficacy trial). The muscle-growth case rests on IGF-1's known biology and animal/tissue work, not on a controlled human trial of this specific analogue. Human efficacy for IGF-1 LR3 is effectively absent.
Primary sources (3)
Is IGF-1 LR3 legal? (Status July 2026)
No legal supervised US route.
What is IGF-1 LR3 used for?
IGF-1 LR3 is marketed for the goals below. See how it ranks against other peptides in each — by evidence, not hype.
What does IGF-1 LR3 cost — and how do you access it legally?
Typical cost
UNKNOWN
No verified legitimate price — IGF-1 LR3 has no legal supervised route and is sold only as a gray-market research chemical, which we don't quote or link.
No legal supervised access route right now.
IGF-1 LR3 has no compliant US route today. Vials sold "for research use only" are a gray-market fig-leaf, not a legal loophole — we don't link them. If you pursue IGF-1 LR3, do it with a licensed clinician, and re-check its legal status first.
Is IGF-1 LR3safe? Side effects & risks
No human efficacy or safety trials for IGF-1 LR3 specifically. Predictable IGF-1-axis risks apply from the drug class: hypoglycemia, edema, and a theoretical cancer-promotion concern from sustained IGF-1 receptor activation. It is sold only as a gray-market research chemical with no legal supervised US route, and it is WADA-prohibited (S2) at all times.
Medical disclaimer: This page is independent editorial information, not medical advice, and Best Peptide For That is not a medical provider. We do not provide dosing. Talk to a licensed clinician before starting, stopping, or changing any peptide or medication. Full medical disclaimer.
FAQ
IGF-1 LR3 FAQ
Does IGF-1 LR3 build muscle?
There is no published human trial showing IGF-1 LR3 builds muscle. The case for it rests on IGF-1's known biology and animal/tissue data — not a controlled human study of this specific analogue — so on our scale it is Grade D, unproven in humans.
Is IGF-1 LR3 legal?
There is no legal supervised US route. IGF-1 LR3 is not FDA-approved and not legally compoundable — it's sold only as a gray-market research chemical. It is also banned in sport: WADA prohibits IGF-1 and all its analogues under S2 at all times.
Is IGF-1 LR3 banned in sport?
Yes. WADA explicitly prohibits IGF-1 and its synthetic analogues (which includes IGF-1 LR3) under S2 — growth factors — banned at all times, in and out of competition, regardless of dose or route.
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