IGF-1 LR3 vs Mecasermin

Written by Aaron CuhaReviewed Sep 2026

The short answer

An approved IGF-1 medicine and a grey market copy of the same hormone. Mecasermin is approved only for children who are not growing because they make far too little IGF-1, and 49 percent of those patients had low blood sugar. IGF-1 LR3 has animal work and no approval, and the low blood sugar risk does not go away just because the label is missing.

IGF-1 LR3 people: 0
IGF-1 LR3 nulls: 0
Mecasermin people: 76
Mecasermin nulls: 0

Dose

No human dose established

Amounts that circulate in forums and on vendor pages are not a human dose. No published study on this page has given this compound to people and reported a result.

Commonly reported amounts, in mcg. IGF-1 LR3 has no approved label and no human dosing trial.

Amounts commonly reported by people buying IGF-1 LR3, recorded for this archive's reconstitution calculator, are 20, 40, 50 and 100 mcg. They are self-reports rather than trial doses, and this archive does not recommend any of them. No human dose has been established for IGF-1 LR3.

Amounts commonly reported by people buying IGF-1 LR3, in mcg, recorded for this archive's reconstitution calculator. Self-reports, not trial doses, and not a recommendation.
Reported amount	Where the number comes from
20 mcg	Commonly reported, no published human dosing trial
40 mcg	Commonly reported, no published human dosing trial
50 mcg	Commonly reported, no published human dosing trial
100 mcg	Commonly reported, no published human dosing trial

Dose

Approved medicine. No human dose established for unlabelled uses

Labeled amounts sit on the prescribing information. This page records what trials measured, not a personal dose.

FDA-approved. INCRELEX (mecasermin), BLA 021839, made by Ipsen, first approved 30 August 2005, prescription only. It is for children who are not growing because of a severe IGF-1 shortage that is not caused by low growth hormone. It is also for children missing the growth hormone gene whose immune system has started blocking growth hormone treatment. It is not approved for adults, for age-related muscle loss, for recovery or for any performance use.

First-hand reports are counted on each profile and never added together. This page sets two published records side by side. It does not pick a winner.

Column A

IGF-1 LR3

Long R3 Insulin-like Growth Factor 1

A long-lasting, lab-made form of IGF-1. It has only been studied in animals, for muscle growth and repair.

Column B

Mecasermin

Mecasermin (Increlex), recombinant human IGF-1

An approved medicine, but only for a rare condition in children. In 76 children with a severe shortage of IGF-1, growth sped up from 2.8 cm a year to 8.0 cm a year in the first year, and 49 percent had low blood sugar. Children followed to the end of puberty moved a good way up the height chart but stayed well short of average.

Side by side, on the facts we can check

What we compare	IGF-1 LR3	Mecasermin
Category	Growth Hormone	Growth Hormone
FDA status	Not FDA-approved	FDA-approved. INCRELEX (mecasermin), BLA 021839, made by Ipsen, first approved 30 August 2005, prescription only. It is for children who are not growing because of a severe IGF-1 shortage that is not caused by low growth hormone. It is also for children missing the growth hormone gene whose immune system has started blocking growth hormone treatment. It is not approved for adults, for age-related muscle loss, for recovery or for any performance use.
Half-life	~20-30 hours	Short, and shorter in the patients it treats. The circulating hormone is normally bound almost entirely to its binding protein and the acid-labile subunit, which extends its persistence enormously; in severe primary deficiency those binding proteins are low, so the administered hormone is cleared faster. This is why the approved product is injected twice daily with food rather than once a day.
Molecular weight	9,111 Da	7,649 Da. A single chain of 70 amino acids with three intramolecular disulfide bridges, per the INCRELEX product label.
How it works	It switches on the IGF-1 receptor. That tells cells to grow, divide and make protein. Because it does not stick to its usual carrier proteins, it keeps working longer.	Mecasermin locks onto the IGF-1 receptor on cells. That switches on growth signals inside the cell, called PI3K/Akt and MAPK. They drive cell growth, protein building and, at the growth plates, bones getting longer. It also fits the insulin receptor fairly well. That is the direct reason low blood sugar is its main side effect, and why it is given with a meal. The body's own IGF-1 travels in the blood almost entirely bound to carrier proteins, IGFBP-3 and one called the acid-labile subunit. Building that carrier depends on growth hormone signals. In a severe primary IGF-1 shortage those signals are broken, so the carrier proteins are low. After a shot, more IGF-1 is free, and it is cleared faster than the body's own would be. That is the real difference between replacing IGF-1 and making it yourself.
Studies in people	1	5
Evidence	Preliminary: 1 human study where nobody was given it	Limited: 1 completed trial, 76 people given it
Legal status, US	Not approved; research use only	FDA-approved, prescription only

open the IGF-1 LR3 profile open the Mecasermin profile

Frequently asked questions

What is the difference between IGF-1 LR3 and Mecasermin?

IGF-1 LR3: A long-lasting, lab-made form of IGF-1. It has only been studied in animals, for muscle growth and repair. Mecasermin: An approved medicine, but only for a rare condition in children. In 76 children with a severe shortage of IGF-1, growth sped up from 2.8 cm a year to 8.0 cm a year in the first year, and 49 percent had low blood sugar. Children followed to the end of puberty moved a good way up the height chart but stayed well short of average.

Which has stronger research evidence, IGF-1 LR3 or Mecasermin?

Each compound gets a band worked out from facts we counted, with the math shown. IGF-1 LR3 is Preliminary (1 human study where nobody was given it). Mecasermin is Limited (1 completed trial, 76 people given it). That counts how much has been done in people. It does not rate whether either one works, and neither one is called the winner.

Are IGF-1 LR3 and Mecasermin FDA-approved?

IGF-1 LR3: Not FDA-approved. Mecasermin: FDA-approved. INCRELEX (mecasermin), BLA 021839, made by Ipsen, first approved 30 August 2005, prescription only. It is for children who are not growing because of a severe IGF-1 shortage that is not caused by low growth hormone. It is also for children missing the growth hormone gene whose immune system has started blocking growth hormone treatment. It is not approved for adults, for age-related muscle loss, for recovery or for any performance use..

Reviewed Sep 2026. This page puts two published records side by side. It is for learning, and it is not medical advice. When this site shows a dose, it is the dose a trial or a clinic actually used, or what people say they did, with the source attached. None of it tells you what to take.