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Explore  /  IGF-1 LR3 (Long R3 IGF-1)

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IGF-1 LR3 (Long R3 IGF-1)

F

lead outcome

IGF-1 LR3 for muscle building in humans (the…

grades vary by outcome ↓

Protein (not a peptide)⚠ WADA-banned

also called — IGF-1 LR3 · Long R3 IGF-1 · Long Arg3 IGF-1 · LR3-IGF-1 · a synthetic analog of Insulin-like Growth Factor 1. INCI: none

muscle / anabolic (research)cell-culture growth factor (its actual established use)

Reference entry — not sold here. The muscle world's hyperplasia dream — building new muscle fibres, not just bigger ones — and the honest reality behind it. Three things up front: it's a protein, not a peptide; there are zero human trials of it for muscle; and the safety profile is genuinely serious. No dosing published here.

In brief

IGF-1 LR3 is a long-acting engineered version of IGF-1, prized in the muscle community for one genuinely special property — hyperplasia, the formation of new muscle fibres via satellite cells, which steroids cannot do. But the honest reality is stark: it was created as a cell-culture reagent, no human trial has ever tested it for muscle or anything else, the hyperplasia effect in humans is debated, and its safety profile — hypoglycemia, tumour-promotion risk, organ overgrowth — is serious. Thrilling mechanism; unproven and genuinely risky product. Banned in sport.

Legal standing, by region

International

See note

- Everywhere — not approved for muscle, performance or anti-aging. Native IGF-1 (mecasermin / Increlex) is FDA- and EMA-approved for pediatric severe primary IGF-1 deficiency only; IGF-1 LR3 is not separately authorised for anything therapeutic — it is a research / cell-culture reagent sold gray-market for bodybuilding. - ⚠ Sport: WADA-prohibited at all times — Section S2 (Peptide Hormones, Growth Factors); validated LongR3-IGF-I detection assays exist. Banned in and out of competition.

⚠ WADA-prohibited in sportSport: WADA-prohibited at all times — Section S2 (Peptide Hormones, Growth Factors); validated LongR3-IGF-I detection assays exist (Mongongu 2020). Banned in and out of competition.

Evidence, by outcome

How we grade →

An honest grade per outcome — drawn from the evidence, not any catalogue. Hype and undemonstrated marketing claims grade low.

OutcomeEvidence base · effectGrade

Muscle hypertrophy + hyperplasia via IGF-1R (the biology)

The biology, in a dish and in animals — not injected LR3 in humans

Cell culture + animal models · Anabolic; satellite-cell activation; new fibres

—

IGF-1 LR3 for muscle building in humans (the marketed use)

Zero human trials for any endpoint; it's a cell-culture reagent

None · Not demonstrated

F

Hyperplasia in humans specifically

Established in vitro/animal; human extent at realistic doses is disputed

Debated · Uncertain

D

Native IGF-1 (mecasermin) — pediatric IGF-1 deficiency

Native form, rare pediatric indication — not LR3, not muscle

FDA/EMA-approved · Improves growth velocity

—

Safety

Hypoglycemia (primary acute risk; with insulin → hospitalisations reported); tumour promotion — LR3 is engineered to evade the IGFBP system that normally reins IGF-1 in, an unstudied long-term oncogenic concern; acromegaly-like organ growth; insulin resistance; gray-market misfolding/endotoxin; WADA-banned

Mecasermin record + IGF-1R pharmacology · Serious concerns

—

Disclosure

Vallydia sells its own cosmetic serums, and some ingredients graded here belong to the same categories as those products. Grades are drawn from the published evidence by the method we publish, and applied to our own ingredients on the same terms — our copper-peptide serum is graded no more kindly than the peptides it competes with. We disclose the interest so you can weigh it.

Trade names shown here (for example Matrixyl, Argireline, Syn-Ake) are the property of their respective owners and are used only to identify the ingredient under discussion. Their appearance implies no affiliation with, or endorsement by, the proprietor.

Evidence changes

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We track new research and update these grades as the evidence moves. Leave your email and we'll tell you if the evidence for IGF-1 LR3 (Long R3 IGF-1) changes - nothing else.

The honest part

the hyperplasia idea is real and genuinely exciting — but it's proven in a Petri dish and lab animals, and the exact molecule you'd buy was designed to grow cells in that dish, not muscle in you. Zero human trials, a hypoglycemia risk that has put people in hospital, and — because it's built to evade the very system that normally keeps IGF-1 in check — a cancer concern that is essentially unstudied over the long term. Respect the mechanism; don't trust the vial.

Identity

an 83-amino-acid engineered analog of IGF-1 (native IGF-1 is 70 aa; ~9 kDa) with two changes — an arginine for glutamic acid at position 3 ("R3") and a 13-amino-acid N-terminal extension ("Long"). Together these cut its binding to IGF-binding proteins (IGFBPs) by ~100–1000×. Since ~98–99% of native IGF-1 is normally sequestered by IGFBPs (half-life ~10–20 min), evading them makes LR3 far more potent and long-lasting — half-life ~20–30 hours. At 83 aa it is a protein, above the "peptide" range, with three disulfide bonds — which is exactly why gray-market "IGF-1 LR3" is hard to fold, verify and trust.

Mechanism (as proposed)

IGF-1 LR3 binds the IGF-1 receptor (a receptor tyrosine kinase) → PI3K/Akt/mTOR (protein synthesis, survival, glucose uptake) and MAPK/ERK (proliferation) → in muscle, satellite-cell activation and new myonuclei/fibres. It also cross-reacts with the insulin receptor (lower affinity) → the hypoglycemia risk. The LR3 modifications let it slip past IGFBPs, so it stays free and active far longer than native IGF-1 — the same property that makes it potent is what makes its off-target and oncogenic risks harder to contain.

Sources — 4 cited

01Chernausek SD, et al. (Mecasermin long-term treatment in severe primary IGF-1 deficiency — efficacy and adverse-effect profile: hypoglycemia, tonsillar hypertrophy, intracranial hypertension.) 2007.

02Conlon MA, Tomas FM, et al. Long R3 IGF-I infusion stimulates organ growth… in the guinea pig. J Endocrinol. 1995.

03Voorhamme D, Bhatt RR. LongR3-IGF-I as a more potent alternative to insulin in serum-free cell culture. Mol Biotechnol. (its actual use.)

04Mongongu C, et al. (Validated detection assay for LongR3-IGF-I / R3-IGF-I in athlete samples.) 2020.

Updated 2026-07-13

Grades reflect the published evidence, not our interest. No dosing, reconstitution, or administration is published for research compounds — that restraint is deliberate.

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This site provides neutral scientific reference and sells only products lawful in your region. Nothing here is medical advice, a recommendation, or an offer to supply unapproved medicines. No dosing or administration is published for research compounds. Cosmetic peptides per Regulation (EC) 1223/2009. Unapproved injectable peptides are neither sold nor advertised in the EU (Directive 2001/83/EC, Title VIII). © 2026 Vallydia.