How each label is mixed
Somatropin, the growth hormone in HGH medicines, comes as a powder that is mixed with a diluent before use. Each FDA label gives the diluent, how much of it goes in and, for most, the strength after mixing.
| Medicine | Diluent | After mixing |
|---|---|---|
| Genotropin 5 and 12 mg cartridgeslabel | In the cartridge’s rear chamber, mixed in the Genotropin Pen 5 or Pen 12 | 5 or 12 mg/mL, 1 mL delivered |
| Humatrope 6, 12 and 24 mg cartridges (18, 36 and 72 IU)label | The syringe of diluent packed with the cartridge, about 3 mL, for its HumatroPen | 2.08, 4.17 or 8.33 mg/mL |
| Omnitrope 5.8 mg viallabel | 1.14 mL of bacteriostatic water with 1.5% benzyl alcohol, packed with the vial | 5 mg/mL |
| Serostim 4 mg viallabel | 0.5 to 1 mL of bacteriostatic water with 0.9% benzyl alcohol | Not printed: the mg ÷ the mL |
| Serostim 5 and 6 mg vialslabel | 0.5 to 1 mL of sterile water | Not printed: the mg ÷ the mL |
Omnitrope also comes ready mixed, in pen cartridges of 5 mg/1.5 mL and 10 mg/1.5 mL. The calculator is for a vial drawn up with a U-100 insulin syringe. Genotropin and Humatrope cartridges are mixed and given in their own pens, as their instructions say; those pens are not in the calculator’s Pen list, which holds reusable U-100 insulin pens.
Mixing a vial
- Draw the diluent into a syringe: the mL on the label, or the water you entered above.
- Inject it with the stream aimed at the glass wall of the vial, not at the powder, so it does not foam.
- Swirl the vial gently until the powder has dissolved. Do not shake it.
- Use it only if it is clear, or slightly opalescent, with no cloudiness or particles.
- Keep it as its label says: a mixed Omnitrope vial in a refrigerator, used within 21 days; a Serostim 4 mg vial mixed with bacteriostatic water at 2 to 8 °C (36 to 46 °F) for up to 14 days. Serostim 5 and 6 mg vials mixed with sterile water are used at once, one dose per vial.
Steps 2 to 4 are the Serostim label’s. The Omnitrope label also says to swirl gently and not to shake, as shaking may break down the hormone.
IU and mg
1 mg of somatropin is 3 IU. The WHO International Standard for somatropin defines its activity as 3.0 IU per mg, and the Humatrope label gives its cartridges as 6 mg (18 IU), 12 mg (36 IU) and 24 mg (72 IU). US labels give doses in mg: a dose in IU divided by 3 is the dose in mg.
Choose IU or mg for the vial and for the dose above; the calculator turns one into the other at 3 IU per mg.
The example in the calculator. A 5 mg vial with 1 mL of water is 5 mg per mL, or 15 IU per mL, the strength of a mixed Omnitrope vial. The dose of 0.6 IU is 0.2 mg, the adult starting dose in the table below: 0.2 ÷ 5 = 0.04 mL, which is 4 units on a U-100 syringe, and the vial holds 25 such doses.
Label doses in units
For adults with growth hormone deficiency, the Genotropin, Humatrope and Omnitrope labels give a dose that does not depend on body weight: about 0.2 mg a day to start, within 0.15 to 0.3 mg, raised every 1 to 2 months by about 0.1 to 0.2 mg a day as the clinical response and IGF-1 levels require.
| Dose | at 2.5 mg/mL | at 5 mg/mL | at 10 mg/mL |
|---|---|---|---|
| 0.15 mg0.45 IU | 6 | 3 | 1.5 |
| 0.2 mg0.6 IU | 8 | 4 | 2 |
| 0.3 mg0.9 IU | 12 | 6 | 3 |
Children’s doses go by body weight, in mg per kg a week, divided into 6 or 7 daily injections on the Genotropin and Omnitrope labels, so the prescriber gives the daily amount. Serostim, for adults with HIV and wasting, is about 0.1 mg per kg once a day: 4, 5 or 6 mg by body weight on its label (2026-07-29).
Other calculators
- Peptide reconstitution calculatorThe water to add to the vial so your dose is the number of units you want to draw.
- Insulin syringe units to mLUnits on a U-100 insulin syringe in mL, and mL in units.
- Peptide calculatorUnits to draw for your dose, from the peptide in the vial and the water you added.
- NAD+ injection calculatorUnits to draw for an NAD+ dose, from the mg in the vial and the mL of liquid in it.
Questions
How many IU are in 1 mg of HGH?
3 IU. That is the activity the WHO International Standard for somatropin defines, and the Humatrope label lists 6 mg as 18 IU. So 0.6 IU is 0.2 mg, and 10 IU is 3.33 mg.
How much water goes into an HGH vial?
The label’s: 1.14 mL of its own diluent for an Omnitrope vial, 0.5 to 1 mL for Serostim. For another vial the water only sets the strength: a 5 mg vial with 1 mL is 15 IU per mL, with 2 mL 7.5 IU per mL, so the same dose takes twice the units. The reconstitution calculator finds the water for the units you want per dose.
Sterile or bacteriostatic water?
The one on the label. Serostim 5 and 6 mg vials take sterile water and are used at once, one dose per vial. A Serostim 4 mg vial takes bacteriostatic water with 0.9% benzyl alcohol and keeps for 14 days in a refrigerator; its label uses sterile water instead for anyone allergic to benzyl alcohol and in pregnancy and breast-feeding. The Omnitrope diluent holds 1.5% benzyl alcohol, and the mixed vial is used within 21 days.
My label gives the strength after mixing. What do I enter?
The strength as mg in 1 mL: for a mixed Omnitrope vial at 5 mg/mL, enter 5 mg and 1 mL. The units are then right for that strength; the doses in the vial are counted for 1 mL.
Sources
- Genotropin (somatropin) Prescribing InformationPfizer, FDA label 2025-07-11. Cartridges and their strength after mixing; adult starting dose; children’s weekly dose in 6 or 7 injections.
- Humatrope (somatropin) Prescribing InformationEli Lilly, FDA label 2025-11-28. Cartridges in mg and IU, their diluent and strength after mixing; adult starting dose.
- Omnitrope (somatropin) Prescribing InformationSandoz, FDA label 2025-07-11. The 5.8 mg vial, its diluent, 5 mg/mL after mixing and 21 days of use; adult starting dose.
- Serostim (somatropin) Prescribing InformationEMD Serono, FDA label 2026-07-29. Vials, diluents and mixing steps; storage; doses by body weight.
- Bristow AF, Jespersen AM. The Second International Standard for somatropinBiologicals 2001;29(2):97–106, PubMed 11580214. The WHO standard’s activity, 3.0 IU per mg.
- BD Insulin Syringe, 510(k) K190054FDA, cleared 2019-10-21. U-100 syringes of 0.3, 0.5 and 1 mL and their lines.