Question 1

What is an International Unit (IU)?

Accepted Answer

International Unit (IU) is a measure defined by the World Health Organization (WHO) to standardize the biological activity of substances that do not have the same potency per mass across different batches — such as peptide hormones (hGH, hCG, FSH, LH), insulin and some vitamins. Each molecule has its own mg/IU equivalence, established in a biological assay against an international reference preparation (e.g. NIBSC).

Question 2

Why do hGH and hCG have such different factors?

Accepted Answer

Because each molecule has a distinct mass-to-biological-activity relationship. The WHO defines, via International Standard (IS), how many IU correspond to 1 mg of pure protein: for hGH it is about 3 IU/mg (IS 98/574); for hCG it is approximately 10,000 IU/mg (IS 99/688). The choice of standard came from the historical comparison against the original urinary preparation. It is not intuitive, but it is internationally consistent.

Question 3

Can I use this calculator for generic somatropin and biosimilars?

Accepted Answer

Yes — provided the product is labeled in IU or mg following WHO standards. Recombinant somatropins (Genotropin®, Humatrope®, Norditropin®, Saizen®, Omnitrope®) and their biosimilars follow the same ≈ 3 IU/mg factor. However, specific batches may show small potency variations declared on the label — always check.

Question 4

Why does insulin have a complicated factor (1 mg ≈ 28.85 IU)?

Accepted Answer

The historical definition fixes 1 IU of insulin at 0.0347 mg of pure recombinant human insulin (WHO IS 83/500 and 86/612). That equals about 28.85 IU per 1 mg. Since insulin is marketed in standardized concentrations (U-100 = 100 IU/mL) and pens count units directly, mg conversion rarely appears in clinical use — but is essential for research and quality control.

Question 5

Can I use this for peptides like BPC-157, TB-500 or Ipamorelin?

Accepted Answer

No. BPC-157, TB-500, Ipamorelin and most therapeutic peptides listed on the platform are dosed exclusively in micrograms (µg) or milligrams (mg) — there is no WHO-defined International Unit for them. IU ↔ mg conversion only applies to substances with a published International Standard, as the ones listed in this tool.

Question 6

Does this calculator prescribe doses?

Accepted Answer

No. It is a strictly educational tool to understand equivalence between units of measurement defined by WHO. It does not replace labels, medical prescription, individualized evaluation or clinical monitoring. Therapeutic decisions require a licensed professional.

mg ↔ International Units (IU) Dose Converter

Equivalent result

How the conversion is done

Why does the factor differ between molecules?

Essential notice