Library / Growth hormone

IGF-1 LR3

Also known as Long R3 IGF-1, LR3-IGF-I

Animal studies only

Modified form of insulin-like growth factor 1 with a longer half life, made for cell culture research. No published clinical studies in humans; it has been detected in black market products.

Not an approved medicine. IGF-1 LR3 is not an approved medicine for this use in Australia or the United States. This page summarises published research for information only. It is not a recommendation to use IGF-1 LR3, and VialOwl does not sell or supply it.

Background

Long R3 IGF-I is a genetically engineered form of insulin-like growth factor 1 made in bacteria, with an arginine in place of glutamate at position 3 and a 13 amino acid extension. It was developed in Adelaide, South Australia, in the early 1990s as a potent reagent for cell culture research.

How it is thought to work

Activates the IGF-1 receptor like natural IGF-1, but binds poorly to the IGF binding proteins that normally hold IGF-1 in check, so it is more potent and lasts longer in the body.

What is claimed, and the evidence

Claim	Evidence	Notes
Stimulating cell growth in laboratory culture	Animal studies only	Its intended research use; more potent than IGF-1 in cell studies.
Promoting growth in livestock	Animal studies only	In pigs it actually reduced growth and suppressed growth hormone and natural IGF-1.
Muscle growth, fat loss and recovery in people	No published evidence	Marketed in bodybuilding; no published human studies.

Side effects

Effect	How often	Notes
Low blood sugar (hypoglycaemia) Serious	Frequency unknown	No LR3 human data; hypoglycaemia is the most common adverse event with approved recombinant IGF-1 (mecasermin) and is expected from its biology.
Suppression of natural growth hormone and IGF-1	Frequency unknown	Seen in pigs given LR3.
Injection site reactions, fluid retention, joint pain	Frequency unknown	Reported for IGF analogues in reviews of self administration.
Possible promotion of tumour growth Serious	Frequency unknown	Biologically plausible because IGF-1 drives cell growth; unproven in people.

Warnings

There are no published human studies of IGF-1 LR3; any human use is experimental.
A black market vial tested in Germany contained a His-tagged laboratory version never intended for injection.
Can cause dangerous low blood sugar, especially with insulin or fasting, based on the effects of related IGF-1 medicines.
Unapproved products bought online or from compounders may be contaminated, non sterile, underdosed, overdosed or contain a different substance; the TGA warns their labelling may be inaccurate and it has received reports of severe allergic reactions and hospitalisations.

Regulatory status

Australia: Not included on the ARTG (unapproved). Schedule 4 in the Poisons Standard under the class entry for insulin-like growth factors, with Appendix D clause 5 possession controls.
United States: Not FDA approved. No FDA compounding category entry found.

Sources

Also in Growth hormone

From the VialOwl library, reviewed 26 September 2026. For education and general information. It is not medical advice and not a recommendation to use IGF-1 LR3.