Somatropin IU to MG: How to Convert Growth Hormone Units

Somatropin IU to mg conversion follows one fixed rule: 1 mg of somatropin equals 3 IU, so you divide an IU figure by 3 to get milligrams. A 12 mg pen therefore holds 36 IU, and a 5 mg vial holds 15 IU. That 3-to-1 ratio comes from the World Health Organization standard for recombinant human growth hormone and is used across FDA-approved somatropin brands sold in the United States.

Somatropin IU to MG Conversion Chart

Two formulas cover almost every calculation you will need:

• IU to mg: divide the IU number by 3.
• mg to IU: multiply the mg number by 3.

The table below shows the conversions people look up most often, from single units to full pen strengths.

International Units (IU)	Milligrams (mg)
1 IU	0.33 mg
1.5 IU	0.5 mg
3 IU	1 mg
6 IU	2 mg
15 IU	5 mg
30 IU	10 mg
36 IU	12 mg

One milligram of somatropin equals 3 IU, and one IU equals about 0.33 mg. Rounding 0.33 mg to 0.3 mg is fine for quick mental math but not for measuring a dose.

Why Somatropin Is Measured in IU Instead of Milligrams

An international unit measures biological activity, while a milligram measures mass. Growth hormone was originally extracted from human pituitary tissue, and potency varied from batch to batch, so regulators described it in IU rather than by weight alone.

Recombinant somatropin is now highly purified, and the WHO assigned a fixed standard of 3 IU per mg. That fixed ratio is why the conversion math is so simple today.

Other hormones do not share this ratio. Insulin runs roughly 28 IU per mg, while hCG and erythropoietin use entirely different scales. A somatropin conversion never transfers to another drug.

A small number of labels and older references list about 2.7 IU per mg. If a product label prints its own IU figure, trust the label over any general chart.

Genotropin 12 mg: How Many IU?

A Genotropin 12 mg GoQuick pen contains 36 IU of somatropin. Pharmacies outside the United States often print the IU value directly on the carton, while US packaging is usually labeled in milligrams only.

Product	Labeled strength	Equivalent IU (at 3 IU per mg)
Genotropin GoQuick pen	12 mg	36 IU
Genotropin cartridge	5.8 mg	17.4 IU
Omnitrope vial	5.8 mg	17.4 IU
Humatrope vial	5 mg	15 IU
Norditropin pen	10 mg	30 IU
Saizen cartridge	8.8 mg	26.4 IU

IU values for brands labeled only in milligrams are calculated at 3 IU per mg. Always match the number printed on your own carton or pen before drawing a dose.

How to Calculate a Dose in IU or mg

Converting a prescription takes about a minute when you work through it in order.

1. Check which unit your prescription uses. US prescriptions are typically written in mg; many other countries use IU.
2. Apply the 3-to-1 rule. A 0.3 mg daily dose equals 0.9 IU, and a 2 IU dose equals about 0.67 mg.
3. Confirm the concentration after mixing. A 5 mg vial reconstituted with 1 mL contains 5 mg/mL, or 15 IU/mL.
4. Multiply concentration by the volume you draw. Drawing 0.1 mL from a 15 IU/mL solution delivers 1.5 IU, which is 0.5 mg.
5. Verify with your prescriber or pharmacist before changing anything. Pediatric and adult regimens differ widely, and dose changes should never be self-directed.

Reconstitution, Concentration, and Injection Basics

Adding bacteriostatic water changes concentration, not the total amount of drug in the vial. A 5 mg vial still holds 15 IU whether you add 1 mL or 2 mL of diluent; only the volume you draw changes.

Add 1 mL to a 5 mg vial and you get 5 mg/mL, or 15 IU/mL. Add 2 mL to the same vial and you get 2.5 mg/mL, or 7.5 IU/mL. People learning how to reconstitute somatropin often assume that more water means more hormone, and that is not how it works.

The same concentration math applies to other peptides. Anyone calculating how much bac water to reconstitute 60 mg tirzepatide is solving the identical problem: total drug divided by total diluent volume.

Technique matters too. Step-by-step guidance on how to use somatropin injection covers site rotation, needle size, and storage, and those details affect how consistently the medication is absorbed.

Safety, Labs, and Buying Somatropin

Somatropin is a prescription medication in the United States. It is FDA-approved for specific conditions such as pediatric and adult growth hormone deficiency, Turner syndrome, and short bowel syndrome, and it is not a supplement.

Anything sold without a prescription as research grade or generic HGH carries real risk of contamination, incorrect potency, or no active ingredient at all. People searching for where to buy somatropin should start with a licensed pharmacy and a valid prescription.

Monitoring is part of treatment. Clinicians typically track IGF-1, thyroid function, blood glucose, and A1c, and a full review of somatropin labs to monitor explains why each marker matters.

Common side effects include fluid retention, joint and muscle pain, carpal tunnel symptoms, and elevated blood sugar. Anyone with an active malignancy, uncontrolled diabetes, or certain eye conditions should discuss the risks with a healthcare professional before starting therapy.

COMMON QUESTIONS

Frequently Asked Questions

How many IU is 1 mg of somatropin?

One milligram of somatropin equals 3 IU under the WHO standard for recombinant human growth hormone. Working the other direction, 1 IU equals about 0.33 mg, so a 5 mg vial contains 15 IU.

Genotropin 12 mg is how many IU?

A Genotropin 12 mg GoQuick pen contains 36 IU of somatropin, calculated at 3 IU per mg. Cartridges that are already labeled in IU show the number directly, so check your own carton before converting.

How do I convert my prescribed somatropin dose from IU to mg?

Divide the IU dose by 3 to get milligrams, or multiply the mg dose by 3 to get IU. A prescription written as 0.6 mg per day is the same as 1.8 IU per day. Confirm the math with your pharmacist, since somatropin doses should only change under medical supervision.