TL;DR: A 100 mcg IGF-1 LR3 vial holds 0.1 mg — one tenth of the more common 1 mg vial — so every downstream number shifts by a factor of ten. Add 1 mL of diluent and you get 100 mcg/mL, which is a tidy 1 mcg per unit on a U-100 syringe: a 20 mcg draw is 20 units. The same 20 mcg from a 1 mg vial in 1 mL would be 2 units. The IGF-1 LR3 calculator handles the conversion; this guide shows the arithmetic behind it, plus the acetic-acid-versus-bacteriostatic-water question that follows the whole IGF family around.
Why 0.1 mg changes every number
IGF-1 LR3 is an 83-amino-acid analogue of insulin-like growth factor 1, carrying an arginine for glutamate swap at position 3 and a 13-residue N-terminal extension (Francis et al., J Mol Endocrinol, 1992). Those two edits gut its affinity for the IGF binding proteins, which is why it behaves as though there is far more free peptide around than the milligram figure suggests. Vendors package it in both 1 mg and 100 mcg presentations, and the smaller vial is not simply “the cheap one” — it is a different math problem.
Almost every reconstitution guide online is written against the 1 mg vial. Copy those numbers onto a 0.1 mg vial and you deliver a tenth of what you intended. Copy them the other way and you deliver ten times. That decimal slip — 100 mcg read as 0.1 mg read as 1 mg — is the single largest source of error in sub-milligram peptides, and it happens on the label, not on the syringe.
For the compound background — how LR3 differs from DES(1-3) and from MGF, and why the three are not interchangeable — see IGF-1 LR3 vs DES vs MGF. The 0.1mg vial page carries the spec sheet.
The reconstitution formula, run on 100 mcg
The formula never changes:
Concentration (mcg/mL) = vial content (mcg) ÷ diluent volume (mL)
And on a U-100 insulin syringe, where 1 mL = 100 units:
mcg per unit = concentration (mcg/mL) ÷ 100
Run those two lines across the volumes people actually use for a 100 mcg vial:
| Diluent added | Concentration | mcg per unit | A 20 mcg dose |
|---|---|---|---|
| 0.5 mL | 200 mcg/mL | 2 mcg | 10 units |
| 1.0 mL | 100 mcg/mL | 1 mcg | 20 units |
| 1.5 mL | 66.7 mcg/mL | 0.67 mcg | 30 units |
| 2.0 mL | 50 mcg/mL | 0.5 mcg | 40 units |
The 1 mL line is the one worth memorising, because it collapses the conversion entirely: at 100 mcg/mL, units equal micrograms. Twenty units is 20 mcg. Fifty units is 50 mcg. There is no mental arithmetic left to get wrong, which is exactly what you want on a vial this small. That property is why 1 mL is the default suggestion in most dilución de IGF-1 LR3 write-ups and why the calculator preselects it.
Compare that to the 1 mg vial: 1000 mcg in 1 mL is 1000 mcg/mL, or 10 mcg per unit. The same 20 mcg target lands on 2 units — a region of the barrel where a half-unit misread is a 25% dosing error. The small vial is not less precise; it is considerably more precise, because it spreads the same dose across ten times more barrel.
At 100 mcg/mL, 20 units on a U-100 syringe = 0.20 mL = 20 mcg. Units and micrograms line up one-to-one.
If unit conversion is the part that trips you up generally, mcg to units on an insulin syringe works through it from first principles across concentrations.
Acetic acid, dilute HCl, or bacteriostatic water
This is the question that follows every IGF analogue, and it is worth separating the chemistry from the convenience.
Research-grade IGF-1 and its analogues are typically lyophilised from acidic solvent systems — acetonitrile with trifluoroacetic acid is common — and supplier datasheets generally direct you to reconstitute in an acidic vehicle: dilute hydrochloric acid around 10 mM, or 0.1% to 1% acetic acid, sometimes sterile water at a stated minimum concentration. The reason is solubility. IGF-1 has an isoelectric point in the mildly acidic range, and the protein dissolves and stays dissolved more readily below it than at neutral pH.
Bacteriostatic water is a different tool. It is sterile water carrying roughly 0.9% benzyl alcohol, and its job is antimicrobial: it lets a vial be entered repeatedly over weeks without organisms establishing. It is near-neutral, so it offers no solubility assistance, but it is by far the more practical choice when a vial will be sampled more than once.
The compromise most laboratory protocols land on is a two-step: dissolve the cake in a small volume of acidic vehicle so it goes fully into solution, then dilute to working concentration in whatever buffer the experiment needs. Applied to a 100 mcg vial that might mean 0.2 mL of dilute acid to wet and dissolve, then 0.8 mL of bacteriostatic water to reach 1 mL and 100 mcg/mL. The arithmetic is unchanged — total volume is total volume — but the peptide sees acid first.
Two practical notes either way. Direct the stream down the vial wall rather than onto the cake; IGF analogues are proteins and shear from a jetted stream is a real degradation route. And swirl, never shake.
Doses per vial, and where the losses hide
This is the part most dosaggio IGF-1 LR3 guides skip. A 100 mcg vial at a 20 mcg working dose is nominally five draws. In practice you will not get five, and the reason is volume that never leaves the system.
At 1 mL fill, five draws of 0.20 mL consume the entire mL with nothing left over for the residue that clings to the vial bottom, the needle hub, and the stopper. Call that residual 30 to 50 µL. At 100 mcg/mL that is 3 to 5 mcg stranded — 3 to 5% of the vial, or roughly a quarter of a dose.
Here is the counterintuitive part: reconstituting in more diluent recovers some of it. Residual volume is roughly fixed by hardware, so at 2 mL the same 40 µL of dead volume carries only 2 mcg instead of 4, because the solution it holds is half as strong. More water means each stranded microlitre costs you less peptide. The trade is a doubled draw volume — 40 units instead of 20 for the same dose — which is usually fine on a U-100 barrel.
Vendor overfill sometimes works in the other direction and quietly gives you back a fraction of a dose. Doses per vial, overfill and dead space covers how to estimate both without guessing.
One more loss route matters specifically at these concentrations: adsorption. Proteins at low concentration bind to glass and plastic surfaces, and 100 mcg/mL is low. Laboratory protocols routinely add a carrier protein — 0.1% human or bovine serum albumin — to reconstituted IGF stocks precisely to occupy those surfaces. A vial reconstituted without carrier and diluted further will lose a non-trivial fraction to the walls of whatever it touches. It is a good argument against over-diluting a sub-milligram vial into a large volume just to get prettier unit numbers.
What the evidence actually supports
Worth being straight about the evidence base, because the dosing math is far more solid than the biology it is being applied to.
LR3’s documented pedigree is preclinical and industrial. Francis and colleagues characterised the analogue in 1992, and Tomas et al., working in dexamethasone-treated rats, reported it was roughly 2.5-fold more potent than IGF-1 at promoting nitrogen retention despite binding the type 1 IGF receptor about three-fold less well — the potency comes from escaping the binding proteins, not from a better receptor fit. Conlon et al. infused LR3 into guinea pigs for seven days and saw increased fractional weight of adrenals, gut, kidneys and spleen, but no stimulation of overall growth, alongside suppressed endogenous IGF-I, IGF-II and IGFBP-3.
That last finding deserves more attention than it usually gets: visceral organ mass moved before anything else did, and the animal’s own IGF axis was suppressed. Commercially, LR3’s largest real-world use is as an insulin replacement in serum-free cell culture media, where it is valued for exactly the stability that makes it interesting elsewhere.
The frequently quoted “20 to 30 hour half-life” circulates widely in vendor material. We have not been able to trace it to a published human pharmacokinetic study, and it should be read as a plausible inference from the reduced IGFBP affinity rather than a measured figure. Human dose-response data for LR3 specifically does not exist in the peer-reviewed literature. Any IGF-1 LR3 Dosierung you see quoted — 20 mcg, 40 mcg, 50 mcg daily — is convention inherited from practice, not a trial-derived number, and this article treats it as an arithmetic input rather than a recommendation.
Frequently Asked Questions
How much bacteriostatic water do I add to a 100mcg IGF-1 LR3 vial?
One millilitre is the most useful choice, because it produces 100 mcg/mL — a concentration where insulin units and micrograms map one to one. Two millilitres halves the strength to 0.5 mcg per unit, doubling your draw size and your resolution. Both are correct; only the unit count changes.
How many units is 20mcg of IGF-1 LR3?
At 100 mcg/mL, which is a 100 mcg vial in 1 mL, 20 mcg is exactly 20 units on a U-100 syringe, or 0.20 mL. Reconstitute the same vial in 2 mL instead and 20 mcg becomes 40 units. Run your own numbers in the IGF-1 LR3 calculator.
Is acetic acid better than bacteriostatic water for IGF-1 LR3?
Acidic vehicles dissolve IGF analogues more readily, which is why datasheets specify dilute HCl or acetic acid. Bacteriostatic water is near-neutral but contains a preservative, so it tolerates repeat entry. No published head-to-head stability comparison for LR3 exists; many protocols dissolve in a little acid, then dilute with bacteriostatic water.
How many doses are in a 100mcg vial of IGF-1 LR3?
Divide 100 by your dose in micrograms — five at 20 mcg, four at 25 mcg, two and a half at 40 mcg. Subtract roughly 3 to 5% for solution stranded in the vial and needle hub, so a nominal five-dose vial realistically yields four full draws plus a partial.
Why do 1mg and 100mcg IGF-1 LR3 vials need different reconstitution volumes?
They do not need different volumes — they produce different concentrations from the same volume. A 1 mg vial in 1 mL is 1000 mcg/mL, ten times stronger, so doses land on 2 or 3 units where a small misread is a large error. The 100 mcg vial spreads the same dose across ten times more barrel.
Can I dilute a 100mcg vial into a larger volume for finer dosing?
You can, but there is a floor. Below roughly 50 mcg/mL, adsorption of the peptide onto glass and plastic surfaces becomes a meaningful share of what you prepared, which is why laboratory stocks add 0.1% albumin as a carrier. Diluting to chase tidier unit numbers can cost more than the precision it buys.
References
- 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.” Journal of Molecular Endocrinology, 1992;8(3):213-223.
- Tomas FM, Knowles SE, Owens PC, Chandler CS, Francis GL, Read LC, Ballard FJ. “Insulin-like growth factor-I (IGF-I) and especially IGF-I variants are anabolic in dexamethasone-treated rats.” Biochemical Journal, 1992;282(Pt 1):91-97. doi:10.1042/bj2820091.
- Conlon MA, Tomas FM, Owens PC, Wallace JC, Howarth GS, Ballard FJ. “Long R3 insulin-like growth factor-I (IGF-I) infusion stimulates organ growth but reduces plasma IGF-I, IGF-II and IGF binding protein concentrations in the guinea pig.” Journal of Endocrinology, 1995;146(2):247-253. doi:10.1677/joe.0.1460247.
- Laajoki L, Le Breton E, Shooter GK, et al. “Secondary structure determination of 15N-labelled human Long-[Arg-3]-insulin-like growth factor 1 by multidimensional NMR spectroscopy.” FEBS Letters, 1997;420(1):97-102.
- Qkine. “Recombinant human IGF-1 LR3 protein (Qk041) — product datasheet.” Reconstitution, storage and stability guidance for lyophilised LR3.
- R&D Systems. “Recombinant Human LR3 IGF-I/IGF-1 GMP — datasheet.” Handling and reconstitution specifications.
This article is a research and educational reference only; IGF-1 LR3 is not an approved medicine, this is not medical advice, and it is not for human consumption.