Most vials in this shop are labelled in milligrams, but HCG says 5000 IU on the label, and that cannot be converted with a universal formula. An international unit measures biological activity, not mass, so its conversion to milligrams is different for every substance. Below is where the difference comes from and how to read the contents of a pack.
What an international unit measures
The international unit, written IU in English and j.m. in Polish, describes the strength of a substance, not its weight. It is set by comparison with a reference standard, so the same number of units can correspond to a different mass depending on which substance we are talking about.
A milligram is a unit of mass and says nothing about activity. With peptides the two are sometimes used interchangeably in everyday speech, and that is the source of a misunderstanding you can see in product descriptions.
Why HCG is given in IU
Chorionic gonadotropin is a glycoprotein hormone, and its activity depends not only on the chain itself but also on the attached sugar groups. Two samples of the same mass can differ in strength, so the contents are described by activity.
The pharmaceutical industry does the same. The approved medicine with this substance is called Pregnyl 5000 IU, giving units, not milligrams. More about the status of this substance is in the guide to HCG.
Three units that are easy to confuse
| Written as | What it means | Where it appears |
|---|---|---|
| mg | Mass of the substance in milligrams | Most vials in the shop, for example 10 mg |
| mcg or µg | Microgram, a thousandth of a milligram | Doses described in studies, for example 300 micrograms |
| IU | Biological activity against a reference standard | HCG 5000 IU, hormonal medicines |
A fourth number comes on top, and it describes the syringe, not the vial. A U-100 insulin syringe has one hundred units per millilitre, so its units describe volume, not strength or mass. The whole calculation is covered in the guide to converting a dose to syringe units.
Why we give no IU to milligram conversion
Because no such conversion exists as a single number. It depends on the substance, its form and the reference standard against which activity was measured. Figures circulating on forums usually refer to a specific preparation, and copied over to another one they stop being true.
For the same reason we do not convert the contents of an HCG vial into milligrams in the product description. We give what the manufacturer gives, 5000 IU, and leave interpretation where it belongs.
How to read it when buying
When comparing two vials of the same substance, look at the same unit on both. HCG 5000 IU by Genheal and HCG 5000 IU by Bio-Peptide both cost 25 EUR, so the comparison is simple. For peptides labelled in milligrams what counts is the price per milligram, not the price of the pack, as the price list for the whole range shows.
The concentration of the solution is a separate matter and does not follow from the label. It only appears on dissolving, whether the contents are given in milligrams or in units, and it is covered in the guide to reconstitution with bacteriostatic water.
Frequently asked questions
How many milligrams is 5000 IU?
There is no single answer. The conversion depends on the substance and the activity standard, which is why the manufacturer gives units, not mass.
How does IU differ from j.m.?
It does not. It is the same notation in two languages: IU in English, j.m. in Polish.
Is mcg the same as mg?
No. A microgram is a thousandth of a milligram, so 300 micrograms is 0.3 mg.
Are the units on a syringe the same units as on a vial?
No. A U-100 insulin syringe has one hundred units per millilitre and measures volume, not activity.
Which products in the shop are labelled in IU?
HCG in 5000 IU vials, from Genheal and from Bio-Peptide. All other items give their contents in milligrams.
This is information about pack labelling, not medical advice. Choosing a dose is up to a doctor.
Sources
- Charakterystyka Produktu Leczniczego Pregnyl 5000 j.m. (Summary of Product Characteristics, in Polish). Polish Register of Medicinal Products. https://leki.urpl.gov.pl/files/Pregnyl_proszekirozpo_5000jm.pdf