Module · Peptides

IGF-1 LR3
Dosage

Mix a vial of IGF-1 LR3 with bacteriostatic water and this gives the concentration, the syringe units for your dose, and what every mark on the syringe holds. Dose is something you enter, not something this suggests.

See the math behind this calculator

FDA status No FDA review found. Increlex, an approved IGF-1 drug, is a different molecule
Size Human IGF-1's 70 amino acids plus 13 added, 83 in all
Human studies None peer-reviewed, a 2026 narrative review says

U-100 syringe
1 mL = 100 units

Milligram
= 1000 mcg

Water added
sets concentration

What IGF-1 LR3 is

IGF-1 LR3 is a lab-made version of insulin-like growth factor-1 (IGF-1). The name is short for long R3 IGF-1, and papers also write it Long [Arg3]-IGF-I or LR3-IGF-I. A 1992 paper describes making it in bacteria. It's the human IGF-1 sequence with the glutamic acid at position 3 swapped for arginine, and with an extension on the front made of the first 11 amino acids of methionyl porcine growth hormone followed by valine and asparagine. A 1993 paper spells the extension out, and it's 13 amino acids long. The label of Increlex, an FDA-approved IGF-1 drug, puts human IGF-1 at 70 amino acids, so 70 plus the 13 added ones is 83.

The 1992 paper tested it on cells. It was more potent than IGF-1 in cell lines that release IGF-binding proteins, and less potent in one that doesn't release detectable amounts. The authors tie the higher potency to how it interacts with those binding proteins. Another 1993 study, from the same research centre, infused IGF-1, LR3-IGF-I and a second variant into diabetic rats. It reported that the two variants were 2.5 to 3 times more potent than IGF-1 in restoring growth, and that other insulin-dependent processes weren't restored. None of these is a study in people.

Where it stands with the FDA

This page found no FDA review of IGF-1 LR3. It isn't in FDA's list of substances nominated for compounding under section 503A, as updated May 14, 2026, under this name or as long R3 IGF-1.

FDA has approved an IGF-1 drug, Increlex (mecasermin), first approved in 2005. Its label says it's for growth failure in children aged 2 and older with severe primary IGF-1 deficiency, or with a growth hormone gene deletion and neutralizing antibodies to growth hormone. The label gives human IGF-1 a molecular weight of 7,649 Da and says the product's amino acid sequence is identical to it. IGF-1 LR3 has a changed sequence, so the Increlex label isn't a label for IGF-1 LR3, and nothing in it is repeated here as if it were.

A narrative review published in Frontiers in Endocrinology in June 2026 is about unregulated peptides marketed as research compounds. It searched publications from January 1989 to January 2026, and says of itself that it isn't a systematic review. It put IGF-1 LR3 in its lowest evidence tier, saying it has no peer-reviewed human studies and is supported only by preclinical extrapolation and grey-literature user narratives.

On safety, the same review says adverse effects reported in off-label settings frequently centre on insulin-like activity, such as symptoms suggestive of low blood sugar. It calls that biologically plausible, and adds that many such reports come from non-clinical sources and should be treated cautiously. It also says data linking higher IGF-1 levels in the blood with increased risk of several cancers are often cited as a reason for concern about IGF-1 analogues, and that this risk should be presented as theoretical but clinically relevant, especially in the absence of long-term safety data for off-label use of them.

Storing IGF-1 LR3

None of the documents behind this page gives a storage condition for IGF-1 LR3, so this page doesn't give one.

This page found no approved label for IGF-1 LR3, so it has nothing official to report on how long a mixed vial keeps.

IGF-1 LR3 dosage calculator questions

How do I turn a IGF-1 LR3 dose into syringe units?

Divide the dose by the concentration to get millilitres, then multiply by 100. A 5 mg vial mixed with 2 mL is 2.5 mg/mL, so one unit on an insulin syringe holds 25 mcg and ten units hold 250 mcg.

How much bacteriostatic water goes in a 5 mg vial of IGF-1 LR3?

There's no single right amount. The water only sets the concentration, and the amount of IGF-1 LR3 in the vial stays the same. With 5 mg, 1 mL makes 5 mg/mL, 2 mL makes 2.5 mg/mL and 3 mL makes 1.667 mg/mL. Choose the amount that puts your dose somewhere between about 10 and 40 units, where it's easiest to read.

Is IGF-1 LR3 approved by the FDA?

This page found no FDA approval or FDA review of IGF-1 LR3. Increlex, an FDA-approved IGF-1 drug, is human IGF-1 itself, which is a different molecule, and IGF-1 LR3 isn't in FDA's list of substances nominated for compounding as updated May 14, 2026. A 2026 narrative review says IGF-1 LR3 has no peer-reviewed human studies.

Does this page tell me how much IGF-1 LR3 to take?

No. This page found no FDA-approved IGF-1 LR3 product, and a 2026 narrative review says IGF-1 LR3 has no peer-reviewed human studies, so this page has no label dose or trial dose to report. The dose box starts empty for that reason, and the chart only converts.

Is IGF-1 LR3 the same as IGF-1?

No. The 1992 paper that describes it says it's the human IGF-1 sequence with arginine in place of glutamic acid at position 3, plus an extension on the front. Increlex, an FDA-approved IGF-1 drug, has a sequence its label calls identical to human IGF-1, so its label doesn't describe IGF-1 LR3.

More peptide calculators by name

The same instrument, set up one peptide at a time. For any other vial, use the peptide reconstitution calculator.

Show the working

Four divisions and a unit conversion, with your own numbers filled in below. If any of it looks wrong, it might be, so tell us what we got wrong.

Concentration after mixing mg per mL = vial mg ÷ water mL

What one syringe unit holds mg per unit = mg per mL ÷ 100

Volume to draw, and the units that's

mL    = dose mg ÷ mg per mL
units = mL × 100

Doses in the vial, and how long it lasts

doses = vial mg ÷ dose mg
days  = doses ÷ doses per day

Constants used

1000 micrograms in a milligram
100 units = 1 mL, the insulin syringe calibration, identical on 0.3, 0.5 and 1.0 mL barrels
10 to 40 units is the band this page treats as comfortable to measure. That's a judgement, not a standard

Note what isn't here. This page has no dose recommendation, potency assumption or half-life. The vial and water boxes start empty, because this page can't know what your vial holds, and the vial sizes in its examples are only examples. The math also treats the water you add as the final volume. Powder takes up a little room of its own, which matters for vials holding a lot of it.

The sources

The arithmetic on this page is exact and needs no source. Everything it says about IGF-1 LR3 does. This page found no FDA review of it, so that comes from the published papers, the label of Increlex, an FDA-approved IGF-1 drug, and FDA's list of nominated substances.

Francis GL, Ross M, Ballard FJ, et al. Novel recombinant fusion protein analogues of insulin-like growth factor (IGF)-I indicate the relative importance of IGF-binding protein and receptor binding for enhanced biological potency. J Mol Endocrinol. 1992;8(3):213-23. PubMed abstract. What the molecule is: the changed amino acid, the extension on the front, and how it compared with IGF-1 in cell tests.
Zhao X, McBride BW, Trouten-Radford LM, Burton JH. Effects of insulin-like growth factor-I and its analogues on bovine hydrogen peroxide release by neutrophils and blastogenesis by mononuclear cells. J Endocrinol. 1993;139(2):259-65. PubMed abstract. The long R3 IGF-I name tied to the molecule, and the extension written out amino acid by amino acid.
Tomas FM, Knowles SE, Owens PC, et al. Insulin-like growth factor-I and more potent variants restore growth of diabetic rats without inducing all characteristic insulin effects. Biochem J. 1993;291(Pt 3):781-6. PubMed abstract. The LR3-IGF-I name and the rat study's findings.
Dominikowski A, Rękoś Z, Olejarz M, et al. The emerging landscape of performance-enhancing peptides modulating GH-IGF1 axis: bridging the gap between clinical evidence and patient self-administration. Front Endocrinol (Lausanne). 2026;17:1822475. Full text on PubMed Central. That it found no peer-reviewed human studies of IGF-1 LR3, the years it searched, that it's a narrative review, and what it says about safety.
Increlex (mecasermin) injection label - DailyMed, National Library of Medicine. What Increlex is: 70 amino acids, identical to human IGF-1, its approval year and what it's approved for. It isn't a label for IGF-1 LR3.
FDA. Bulk Drug Substances Nominated for Use in Compounding Under Section 503A, updated May 14, 2026. FDA's running list of nominated substances and its three categories. Checked for this peptide by name; it isn't in any of them.
Humulin R U-100 label - DailyMed, National Library of Medicine. The syringe scale this page converts into: 100 units per mL, the same on 0.3, 0.5 and 1.0 mL barrels.

None of these documents contains a dose recommendation that applies to you, and neither does this page. They're listed so every statement here can be checked against where it came from.