HGH Calculator: Dosage in IU, mg and Syringe Units
This HGH calculator converts somatropin from mg to IU at 3 IU per mg, then turns IU into mL and U-100 syringe units for your vial and water volume. For example, a 5 mg vial mixed with 2 mL of water holds 15 IU, and 1 mg of it is 3 IU, 0.4 mL or 40 units on a U-100 syringe. The 3 IU per mg factor matches the Humatrope label, which lists its 6 mg cartridge as 18 IU. The calculator does the arithmetic only; it does not pick an amount for you.
Short answer
- How many IU are in 1 mg of HGH?
- About 3 IU. The second international standard for somatropin defines 3.0 IU/mg, and Humatrope lists 6 mg as 18 IU. The same label also writes 0.1 mg/kg as 0.27 IU/kg, about 2.7 IU per mg.
- How do I get syringe units?
- Divide the amount by the vial strength (mg per mL) to get mL, then multiply by 100. On a U-100 syringe, 100 units fill 1 mL.
- Are syringe units the same as IU?
- No. Syringe units mark volume. MedlinePlus describes U-100 syringes for insulin and does not say they are used for somatropin.
Sources: Second International Standard for somatropin, Biologicals 2001 (PMID 11580214); Humatrope prescribing information (DailyMed); MedlinePlus, Giving an insulin injection
Enter your own numbers
The amount starts at 1 mg. That is an example number for the math, not a dose. Replace it with your own figure.
Read it from the vial or carton.
Zomacton's label allows 1 mL to 5 mL for its 5 mg vial.
Factor used: 3 IU per mg. Syringe units assume a U-100 syringe (100 units in 1 mL).
Result for the numbers you entered
Whole vial
15 IU
5 mg at 3 IU per mg
Strength after mixing
7.5 IU/mL
2.5 mg/mL
Your amount in both units
3 IU
1 mg
U-100 syringe units
40 units
0.4 mL of liquid
Arithmetic only. It assumes the vial holds exactly what the label states and that all the water went in.
How the HGH math works
Three steps turn a figure on a label into a mark on a syringe. Each step is plain division or multiplication.
- mg to IU. Multiply mg by 3. Divide IU by 3 to go back to mg.
- Strength of the mixed vial. Divide the mg (or IU) in the vial by the mL of water you added.
- Volume and syringe units. Divide your amount by the strength to get mL. Multiply mL by 100 for U-100 syringe units.
| Vial and water | Whole vial | Strength | Amount | Volume | U-100 units |
|---|---|---|---|---|---|
| 5 mg in 2 mL | 15 IU | 2.5 mg/mL (7.5 IU/mL) | 1 mg (3 IU) | 0.4 mL | 40 units |
| 5 mg in 1 mL | 15 IU | 5 mg/mL (15 IU/mL) | 1 mg (3 IU) | 0.2 mL | 20 units |
| 5 mg in 5 mL | 15 IU | 1 mg/mL (3 IU/mL) | 1 mg (3 IU) | 1 mL | 100 units |
The same 1 mg reads as 20, 40 or 100 units. It depends on how much water went in. That is why a unit count means nothing without the vial size and water volume next to it. The Genotropin label gives one fixed strength for one of its presentations: after reconstitution, each mL contains 5 mg of somatropin.
Sources: Zomacton prescribing information (DailyMed); Humatrope prescribing information (DailyMed); Genotropin prescribing information (DailyMed)
Why the Humatrope label gives two IU figures
The Humatrope label itself uses two ratios. This calculator uses 3 IU per mg, the figure in the label's cartridge section and in the international standard.
- The dosage forms section lists cartridges of 6 mg (18 IU), 12 mg (36 IU) or 24 mg (72 IU). Each is 3 IU per mg.
- The pharmacokinetics section describes a dose of 0.1 mg/kg (0.27 IU/kg). That is about 2.7 IU per mg.
- The paper that calibrated the second international standard for somatropin says its specific activity should be defined as 3.0 IU/mg.
The gap is about 10 percent. If you are matching a figure written at 2.7 IU per mg, the IU this calculator shows will read a little higher for the same mg. The Genotropin and Zomacton labels state their strengths in mg, so the mg figure on your own product is the one to start from.
Sources: Humatrope prescribing information (DailyMed); Second International Standard for somatropin, Biologicals 2001 (PMID 11580214)
Insulin syringe units are not HGH units
A unit on an insulin syringe measures volume, not hormone. MedlinePlus says standard insulin contains 100 units in 1 mL, called U-100, and that every small notch on a standard 1 mL insulin syringe is 1 unit of insulin. It also says the type of insulin should match the type of syringe.
MedlinePlus describes these syringes for insulin only. It does not say they are used for somatropin. This calculator uses the U-100 marks only as a volume scale: 1 unit equals 0.01 mL. For the full units to mL table, see the insulin syringe units chart, and for barrel sizes, the insulin syringe sizes guide.
What the Humatrope label says about adult dosing
The Humatrope label lists replacement of growth hormone in adults with growth hormone deficiency as its adult use. It states that it is not indicated for the treatment of non-GH deficient adults. No label in this page's sources gives a dose for bodybuilding or anti-aging use.
The Humatrope prescribing information lists these adult starting figures:
- Non-weight based: approximately 0.2 mg/day (range, 0.15 mg/day to 0.3 mg/day)
- Weight based: 0.006 mg/kg daily, increased according to individual patient requirements to a maximum of 0.0125 mg/kg daily
Disclaimer: this is label information for adults with growth hormone deficiency, not a recommendation. Dose decisions belong with a licensed clinician.
The label says to use the patient's clinical response, side effects and age and sex adjusted IGF-1 blood levels to guide dose changes. A calculator cannot see any of those, which is why this one converts numbers and stops there.
The label also warns that fluid retention may occur often during somatropin therapy. It lists swelling, joint pain, muscle pain and nerve compression such as carpal tunnel syndrome, usually short lived and dose dependent. It adds that Humatrope may decrease insulin sensitivity, particularly at higher doses.
Who this calculator is not for
The IU math here applies to somatropin, the hormone itself. Growth hormone releasing peptides are different molecules with no IU on a label, so a mg to IU factor does not apply to them. For what those peptides are, see what HGH peptides are and HGH vs peptides. For mg to mL math on a peptide vial, use the peptide reconstitution calculator.
Common questions
How many IU are in 1 mg of HGH?+
About 3 IU. The paper that calibrated the second international standard for somatropin says its specific activity should be defined as 3.0 IU/mg, and the Humatrope label lists a 6 mg cartridge as 18 IU. The same label also writes 0.1 mg/kg as 0.27 IU/kg, which works out to about 2.7 IU per mg, so the label itself uses both figures. This calculator uses 3 IU per mg.
How do I convert IU of HGH to syringe units?+
Find the strength of the mixed vial in IU per mL (total IU divided by the mL of water added), divide the IU you want to measure by that strength to get mL, then multiply the mL by 100. That last number is the mark on a U-100 insulin syringe, where 100 units fill 1 mL.
Are insulin syringe units the same as HGH IU?+
No. Syringe units are a volume mark: on a U-100 syringe, 100 units equal 1 mL. HGH IU are a measure of the hormone itself. MedlinePlus describes U-100 syringes for insulin only and does not say they are used for somatropin, so the units on the barrel only tell you volume.
How much water do you mix with a 5 mg HGH vial?+
It depends on the product. The Zomacton label says to reconstitute its 5 mg vial with 1 mL to 5 mL of diluent, Bacteriostatic Sodium Chloride Injection with 0.9% benzyl alcohol. More liquid makes a weaker solution, so the same amount of hormone takes up more syringe units.
Does this HGH dosage calculator tell me how much to take?+
No. It only converts a figure you enter. The Humatrope label says dose changes are guided by clinical response, side effects and age and sex adjusted IGF-1 levels, which no calculator can measure. Dose decisions belong with a licensed clinician.
Is HGH approved for adults without growth hormone deficiency?+
Not under the Humatrope label. It lists replacement of growth hormone in adults with growth hormone deficiency as its adult use and states that it is not indicated for the treatment of non-GH deficient adults.
Sources: Second International Standard for somatropin, Biologicals 2001 (PMID 11580214); Humatrope prescribing information (DailyMed); Zomacton prescribing information (DailyMed); MedlinePlus, Giving an insulin injection
Disclaimer: this is general education and arithmetic, not medical advice and not a dosing recommendation.
Related tools and guides
This calculator is for education only and is not medical advice. It converts figures you enter using 3 IU per mg and U-100 syringe marks. It does not recommend any amount, product or use.
Sources
- 1.HUMATROPE (somatropin) prescribing information, Eli Lilly and Company, DailyMed label version 45, published 20 August 2026, retrieved October 2026. Dosage forms section (cartridges of 6 mg (18 IU), 12 mg (36 IU) and 24 mg (72 IU)), pharmacokinetics section (0.1 mg/kg (0.27 IU/kg)), adult dosing, indications, dose titration, fluid retention and insulin sensitivity warnings.
- 2.The Second International Standard for somatropin (recombinant DNA-derived human growth hormone): preparation and calibration in an international collaborative study. Biologicals, June 2001. PMID 11580214. Supports the 3.0 IU/mg specific activity used by this calculator.
- 3.GENOTROPIN (somatropin) prescribing information, Pfizer, DailyMed label version 37, published 4 August 2026, retrieved October 2026. Supports the statement that after reconstitution each mL contains 5 mg of somatropin.
- 4.ZOMACTON (somatropin) prescribing information, Ferring Pharmaceuticals, DailyMed label version 26, published 20 April 2026, retrieved October 2026. Supports the 5 mg vial reconstituted with 1 mL to 5 mL of diluent.
- 5.MedlinePlus (US National Library of Medicine), Giving an insulin injection, updated 21 July 2024, retrieved October 2026. Supports U-100 meaning 100 units in 1 mL, the 1 unit notch on a standard 1 mL insulin syringe, and matching the insulin to the syringe type.