A to Z / Growth hormone

IGF-1 LR3

Also known as Long R3 IGF-1, insulin-like growth factor 1 LR3.

Best known for The long-acting IGF-1 with a serious risk profile

Evidence★☆☆☆☆

Safety dataLargely unknown

Route Injectable

United StatesNot approved

AustraliaSchedule 4 + Appendix D cl.5 (insulin-like growth factors, class entry)

as at 16 September 2026

What it is

IGF-1 LR3 is a modified version of insulin-like growth factor 1: the hormone through which much of growth hormone's effect is delivered. The modifications make it far more active and much longer-lasting than natural IGF-1.

It is a research reagent, developed for cell culture work and not approved for human use, that later moved into bodybuilding use.

What the full entry covers

The book carries the rest of this entry:

Where the research stands, with every claim cited
What people commonly ask, and what the research shows so far
Dosing in four labelled bands, described and not recommended
Side effects, serious risks, cautions and interactions
Questions to discuss with your doctor
How it compares with IGF-1 DES, Somatropin, MK-677, CJC-1295 (with DAC)

Related entries

IGF-1 DESThe short-acting IGF-1 discussed for "site-specific" growth · Evidence ★☆☆☆☆
SomatropinHuman growth hormone itself, the benchmark for every secretagogue · Evidence ★★★★★
MK-677The oral growth hormone secretagogue · Evidence ★★★☆☆
CJC-1295 (with DAC)Half of the classic clinic growth hormone stack · Evidence ★★☆☆☆

A certificate of analysis tells you what is in a vial. The evidence rating above tells you whether the compound has been shown to work in humans. Neither answers the other's question. How to read a certificate of analysis.

This page describes what is known and not known about IGF-1 LR3. It is not medical advice and not a recommendation to use it.