HGH Dosage Calculator: IU to mL to Syringe Units
REVIEWED BY
Marcus Reinhardt — Chemical Researcher, Lead Analyst & Peptide Research Advisor
Marcus Reinhardt is a chemical researcher specializing in sustainable materials and advanced formulation science, with research experience in compound development and health optimization. He reviews all Peptide Insider educational content for scientific accuracy, strength of supporting evidence, and practical relevance. Editorial team.
Written by Marcus Reinhardt · Lead Analyst, Peptide Insider · LinkedIn
Evidence-first peptide coverage — every claim on this page is linked to its primary source and reviewed against our editorial policy
Citations verified against PubMed · Published: 2026-09-07 · Last updated: 2026-09-07
Growth hormone is the one compound on this site whose vials are labelled in international units rather than milligrams, and it is the one where two different things are both called “units”: the IU of somatropin activity printed on the vial and the 0.01 mL syringe unit printed on an insulin syringe. Mixing them up is the most common HGH arithmetic error there is. This HGH dosage calculator converts the IU on your vial and the bacteriostatic water you add into IU per mL, converts an amount you choose in IU into syringe units, and labels every figure so the two kinds of unit never merge.
WHAT THIS TOOL IS, AND IS NOT
It converts the vial size and water volume you enter into a concentration, and converts an amount you choose into insulin-syringe units. Nothing is pre-filled as a dose and nothing on this page recommends one. Somatropin is a prescription drug dosed by titration to blood IGF-I in people with diagnosed deficiency; the trial regimens are summarised below as context, in the milligram terms the trials used.
How the HGH math works
Three steps. First, concentration: international units in the vial divided by millilitres of bacteriostatic water added gives IU/mL. A 10 IU vial with 1 mL of water is 10 IU/mL. Second, what one syringe unit holds: a U-100 insulin syringe has 100 syringe units per millilitre, so one syringe unit is 0.01 mL and holds the concentration divided by 100. At 10 IU/mL, one syringe unit holds 0.1 IU. Third, syringe units to draw: the amount you chose, in IU, divided by the IU in one syringe unit.
The word “unit” is doing two jobs here, and that is where HGH arithmetic goes wrong. An international unit (IU) is a measure of somatropin activity printed on the vial; a syringe unit is a volume mark, 0.01 mL, printed on the barrel. They coincide only when the vial is reconstituted to exactly 1 IU per syringe unit, which is 100 IU/mL. At any other concentration they differ, and the calculator keeps them apart by labelling every figure.
HGH reconstitution chart
The same arithmetic laid out for the IU vial sizes somatropin is commonly sold in, at one, two and three millilitres of bacteriostatic water. “Per unit” is one mark on a U-100 insulin syringe; “per 10 units” is 0.1 mL. These are conversions, not doses.
| Vial | Water added | Concentration | Per unit | Per 10 units |
|---|---|---|---|---|
| 10 IU | 1 mL | 10 IU/mL | 0.1 IU | 1 IU |
| 10 IU | 2 mL | 5 IU/mL | 0.05 IU | 0.5 IU |
| 10 IU | 3 mL | 3.333 IU/mL | 0.033 IU | 0.33 IU |
| 12 IU | 1 mL | 12 IU/mL | 0.12 IU | 1.2 IU |
| 12 IU | 2 mL | 6 IU/mL | 0.06 IU | 0.6 IU |
| 12 IU | 3 mL | 4 IU/mL | 0.04 IU | 0.4 IU |
| 15 IU | 1 mL | 15 IU/mL | 0.15 IU | 1.5 IU |
| 15 IU | 2 mL | 7.5 IU/mL | 0.075 IU | 0.75 IU |
| 15 IU | 3 mL | 5 IU/mL | 0.05 IU | 0.5 IU |
| 36 IU | 1 mL | 36 IU/mL | 0.36 IU | 3.6 IU |
| 36 IU | 2 mL | 18 IU/mL | 0.18 IU | 1.8 IU |
| 36 IU | 3 mL | 12 IU/mL | 0.12 IU | 1.2 IU |
Table values are exact arithmetic (IU ÷ mL; IU per unit = IU/mL ÷ 100). They assume the vial label is accurate, which for research-market products is only established by a batch-matched certificate of analysis.
How growth hormone is actually dosed in adults, and why it is in milligrams
Somatropin (recombinant human growth hormone) is a prescription medicine with decades of trial data in growth hormone deficiency, and those trials are the only human dosing evidence that exists for the compound sold on the research market as “HGH”. Two features of the evidence matter for anyone with a calculator. The trials dosed by milligrams or micrograms per kilogram, titrated to blood IGF-I, not by a fixed number of units; and the modern approach starts low and adjusts, because a fixed body-weight dose overshoots in many people.
| Trial | Population | Regimen | Finding | Source |
|---|---|---|---|---|
| Hoffman 2004, individualised vs fixed dosing (J Clin Endocrinol Metab) | 387 adults with GH deficiency, 32 weeks | Fixed: 4, then 8, then 12 µg/kg/day. Individualised: 0.2 mg/day, raised in 0.2 mg steps to at most 0.8 mg/day according to clinical response and serum IGF-I | Similar efficacy; final doses were higher in the fixed arm (0.70 vs 0.54 mg/day); authors conclude therapy should start low and be titrated to an IGF-I level within the normal range | PMID 15240596 |
| Hoffman 2004, placebo-controlled body-composition trial (J Clin Endocrinol Metab) | 166 adults with adult-onset GH deficiency, 12 months | Started at 0.0125 mg/kg/day, increased to 0.025 as tolerated or decreased to 0.00625 mg/kg/day | After 12 months 79% remained on 0.0125 mg/kg/day and 21% had been reduced; IGF-I in treated men exceeded age-adjusted normal ranges at the same doses that produced a smaller response in women | PMID 15126520 |
Somatropin is standardised so that 1 mg corresponds to 3 IU, which is how a 0.2 mg starting dose in the titration trial becomes 0.6 IU, and how research-market vials labelled 10 IU or 12 IU relate to the milligram figures above. Both trials were in people with a diagnosed deficiency, under endocrinologist supervision, with blood monitoring; nothing in them speaks to use in people with normal growth hormone. And note the second study’s finding about sex: the same weight-based dose overshot IGF-I in men and undershot in women, which is the strongest argument in the literature against reading any fixed IU figure off a chart.
Reconstitution notes that change the numbers
Bacteriostatic water, not sterile water, for multi-draw vials. Bacteriostatic water contains 0.9% benzyl alcohol, which is what allows a reconstituted vial to be entered more than once; sterile water has no preservative. Our bacteriostatic water guide covers the label facts.
Volume added is the number that matters, not the vial’s stated capacity. If you add 2 mL, the concentration uses 2 mL regardless of whether the water vial says 10 mL or 30 mL. Measure the water with the same insulin syringe you will draw with, since 100 units is 1 mL.
Lyophilized powder adds a negligible volume. A few milligrams of peptide dissolved in millilitres of water does not change the volume in a way an insulin syringe can resolve, which is why every calculator, including this one, ignores it.
Label accuracy is the biggest error term. A vial labelled 10 IU that assays at 80% of label contains 8 IU of the stated compound, and every number above shifts with it. This is why a recent, batch-matched third-party certificate of analysis is the minimum standard on Peptide Insider, and why we publish how to read one.
Frequently asked questions
Does this calculator recommend an HGH dose?
No. The amount field is blank until you type into it. The calculator converts the IU on your vial and the water you enter into IU per mL and converts an amount you choose into syringe units. The prescription regimens described on this page were titrated to blood IGF-I in people with diagnosed growth hormone deficiency and are context rather than a recommendation.
How many syringe units is 1 IU of HGH?
It depends on the concentration. As arithmetic only: a 10 IU vial in 1 mL is 10 IU/mL, so 1 IU is 0.1 mL, which is 10 syringe units on a U-100 insulin syringe; the same vial in 2 mL is 5 IU/mL and 1 IU becomes 20 syringe units. Only at 100 IU/mL would one IU equal one syringe unit.
How many IU is 1 mg of somatropin?
Three. The international standard for somatropin sets 1 mg equal to 3 IU, so a 10 IU vial contains about 3.33 mg and a 12 IU vial 4 mg. The trials on this page are reported in milligrams; multiply by three to read them in IU.
Why does the vial say IU when the trials used mg?
International units are a measure of biological activity that predates precise mass measurement of the hormone; modern pharmaceutical somatropin is standardised so the two scales convert exactly, and prescribing shifted to milligrams. Research-market vials kept the IU labelling. The calculator works in IU because that is what the label says.
Is the 'syringe unit' the same as the IU on the vial?
No, and this is the error the page is built to prevent. A syringe unit is a volume, 0.01 mL, marked on the barrel of a U-100 insulin syringe. An IU is an amount of somatropin. How many syringe units hold one IU depends entirely on how much water went into the vial, which is what the calculator works out.
Which syringe size should I select?
The one you actually have. The 30, 50 and 100 options are all U-100 insulin syringes, so one unit is 0.01 mL on each; the setting only changes the capacity ceiling and the drawing. The calculator warns when an amount exceeds the selected syringe or falls below two units, where the markings stop being precise.