FreePeptideCalc

IGF-1 LR3 Dosage Calculator

A laboratory cell-culture reagent. No human trial has ever evaluated it for any endpoint, and its design makes hypoglycaemia the dose-limiting risk.

Written by , who builds and maintains this site and is not a clinician. Every figure links to its primary source.

Not approved

Not approved; never even nominated

IGF-1 LR3 is on no FDA compounding list — not Category 1, 2 or 3. It was never nominated, so the FDA has never evaluated it. It is sold as a research reagent and cell-culture supplement. The approved relative is mecasermin (Increlex), a different molecule, for severe primary IGF-1 deficiency. Any claim that IGF-1 LR3 is available through compounding is false.

No approved human dose exists for this compound in any country. The figures below are the doses used in named published studies, reproduced for reference only. Doses given to rats or mice do not convert to a human dose. The FDA has stated that labelling a product “research use only” or “not for human consumption” does not change its legal status when the seller's own marketing shows it is intended for people.

Anti-doping: Prohibited at all times. WADA class S2.2 — IGF-1 and its analogues are explicitly prohibited.

Calculator inputs

Set up your vial

Enter the label, dilution and dose. The result updates as you type.

Syringe volume
Syringe volume
IGF-1 LR3 in the vial
IGF-1 LR3 in the vial
Research vials are commonly 100 µg or 1 mg
Bacteriostatic water to add
Bacteriostatic water to add
Dose per injection
Dose per injection
No approved human dose exists for this compound. The dose shown is only a calculator input, not a recommendation or starting point.
More optionsReverse calculation, schedule and cost

Enter the bacteriostatic water you added and get the volume to draw.

Draw to
2units(0.02 mL)
2 units01020304050Drag the plunger, or focus it and use the arrow keys
Draw to 2 units on a 50-unit U-100 syringe.
Concentration
1000 mcg/mL
Water added
1 mL
Doses in vial
50
How the concentration is calculated

This divides the peptide by the water you add. The powder occupies a little volume of its own, which is negligible on a typical vial but not on one with a heavy bulking agent. When a product label states a concentration, use the label’s number.

A 2-unit draw is very small. Adding more water raises the volume and makes the dose easier to measure accurately.

Key facts

Molecular weight
9,111 DaNative human IGF-1 is 7649 Da. LR3 is a 70-amino-acid IGF-1 with a Glu3→Arg substitution plus a 13-amino-acid N-terminal extension.
Half-life
Not published. No accessible human pharmacokinetic study reports one, so any specific figure quoted elsewhere has no primary source behind it.
Also sold as
Long R3 IGF-1, LR3 IGF-I

Doses used in published studies

These are reproduced for reference. They are not recommendations, and an animal dose in mg/kg does not convert to a human dose.

ratsubcutaneous, continuous infusion by implanted osmotic pump, 14 days

44 µg/day of LR3IGF-I

Tomas et al., Journal of Endocrinology 1993, in normal growing female rats. That dose produced increases in body weight gain, nitrogen retention and food conversion efficiency comparable to 278 µg/day of native IGF-I — roughly a six-fold potency advantage per microgram. Human GH infused at 213 µg/day did not stimulate body growth at all in the same experiment.

ratcontinuous infusion, 7 days

98 nmol/day per kg body weight

Tomas, Growth Hormone & IGF Research 2001, in young (5-week) and adult (12-week) rats fed at 100%, 78%, 56% or 33% of ad libitum intake. Infused rats held 3–8% more body weight and better nitrogen retention, but muscle protein was not conserved — and in adult rats LR3IGF-I made the food restriction worse, raising protein breakdown and lowering protein synthesis. A weight number and a lean-tissue number pointed in opposite directions.

pigsingle bolus injection

20 and 50 µg/kg body weight

Tomas et al., Journal of Endocrinology 1997, comparing IGF-I with four poorly-IGFBP-binding variants including LR3IGF-I, and with insulin at 3 µg/kg. The variants lowered plasma glucose two- to three-fold more potently than native IGF-I and, at doses equipotent for the glucose nadir, produced about twice the cumulative four-hour hypoglycaemia. This is the study that makes hypoglycaemia, not muscle growth, the dose-limiting property of the molecule.

guinea pigcontinuous infusion, 7 days

120 µg/day

Conlon et al., Journal of Endocrinology 1995, in 350 g female guinea pigs. LR3IGF-I raised the fractional weight of the adrenals, gut, kidneys and spleen, but body weight gain, feed intake, feed conversion efficiency and carcass composition were all unchanged. Selected organs grew; the animal did not.

How good is the evidence?

Zero human trials of any kind. What does exist is a small animal literature from the 1990s — rats, pigs and guinea pigs, almost all of it from one Adelaide group — in which LR3IGF-I was a research tool for probing IGF-binding protein biology, not a candidate drug. The only clinical read-across is the label of a different, weaker, buffered molecule. The substitution and N-terminal extension drop its affinity for IGF-binding proteins by orders of magnitude — normally about 99% of circulating IGF-1 is sequestered by those proteins, and LR3 largely escapes that buffer, so a given mass is far more bioavailable and longer-acting at both the IGF-1 and insulin receptors. That is not a theoretical point: in pigs the variants that bind IGFBPs poorly lowered blood glucose two to three times more potently than native IGF-I and kept it suppressed four to eight times longer. The Increlex label for the far weaker native molecule already requires a meal or snack within 20 minutes of every injection because of hypoglycaemia risk. LR3 has no label, no titration schedule and no monitoring protocol.

Common questions

Sources

Every number on this page comes from one of the documents below. Where no reliable source exists, the page says so instead of filling the gap.

  1. RegulatorFDA· 2026-05-14
    Bulk Drug Substances Nominated for Use in Compounding Under Section 503A
  2. ReferenceR&D Systems
    Recombinant Human LR3 IGF-I — product datasheet (molecular weight, structure)
  3. FDA labelFDA / DailyMed· 2025-05
    INCRELEX (mecasermin) injection, solution — FDA prescribing information
  4. RegulatorWorld Anti-Doping Agency· 2026
    WADA 2026 Prohibited List
  5. RegulatorUSADA
    Peptides, Growth Hormones and Cosmetics
  6. Published studyJournal of Endocrinology 1993;137(3):413–21· 1993-06
    Tomas FM, Knowles SE, Chandler CS, Francis GL, Owens PC, Ballard FJ. Anabolic effects of insulin-like growth factor-I (IGF-I) and an IGF-I variant in normal female rats
  7. Published studyGrowth Hormone & IGF Research 2001;11(2):92–103· 2001-04
    Tomas FM. Insulin-like growth factor-I (IGF-I) analogue, LR(3)IGF-I, ameliorates the loss of body weight but not of skeletal muscle during food restriction
  8. Published studyJournal of Endocrinology 1997;155(2):377–86· 1997-11
    Tomas FM, Walton PE, Dunshea FR, Ballard FJ. IGF-I variants which bind poorly to IGF-binding proteins show more potent and prolonged hypoglycaemic action than native IGF-I in pigs and marmoset monkeys
  9. Published studyJournal of Endocrinology 1995;146(2):247–53· 1995-08
    Conlon MA, Tomas FM, Owens PC, Wallace JC, Howarth GS, Ballard FJ. Long R3 insulin-like growth factor-I infusion stimulates organ growth but reduces plasma IGF-I, IGF-II and IGF binding protein concentrations in the guinea pig
  10. Published studyGrowth Hormone & IGF Research 2010;20(5):386–90· 2010-10
    Kohler M, Thomas A, Walpurgis K, Terlouw K, Schänzer W, Thevis M. Detection of His-tagged Long-R³-IGF-I in a black market product