Erythropoietin (EPO) Unit Converter
Erythropoietin (EPO) Unit Converter
Convert erythropoietin between mIU/mL, IU/L and mIU/L, with the adult reference interval and what a high or low value means.
Erythropoietin (EPO) converter
Activity unitsErythropoietin 12 mIU/mL
Units
- IU
- international unit of biological activity, defined against the WHO standard
- mass units
- not used — EPO is reported by bioactivity, so there is no molar conversion
Worked example
Erythropoietin 12 mIU/mL
12 mIU/mL = 12.0 IU/L = 12,000 mIU/L
Interpretation against haemoglobin
| Haemoglobin | EPO | Interpretation |
|---|---|---|
| Low | High | Appropriate response to anaemia |
| Low | Normal or low | Inappropriately low — renal disease, inflammation |
| High | Low | Polycythaemia vera |
| High | High | Secondary polycythaemia — hypoxia, EPO-secreting tumour, exogenous EPO |
What erythropoietin measures
Erythropoietin is the hormone that drives red cell production, made almost entirely by peritubular interstitial cells in the kidney in response to tissue hypoxia. Plasma levels rise steeply and non-linearly as haemoglobin falls, which is why the result is meaningless without the haemoglobin beside it.
The single most useful application is distinguishing primary from secondary polycythaemia. In polycythaemia vera the marrow is autonomous and EPO is suppressed, so a raised haematocrit with a low EPO points strongly to a JAK2-driven myeloproliferative neoplasm. A raised haematocrit with a high EPO points instead to hypoxia, sleep apnoea, high-altitude residence, an EPO-secreting tumour or exogenous administration.
In the other direction, an EPO level within the reference interval in an anaemic patient is inappropriately low, and this is the biochemical basis of the anaemia of chronic kidney disease. Inflammation also blunts the response, which is part of why anaemia of inflammation responds poorly to iron alone.
Because EPO is measured in units of biological activity rather than mass, there is no molar conversion — mIU/mL and IU/L are the same number.
Frequently asked questions
Is mIU/mL the same as IU/L for erythropoietin?
Yes, exactly. The two are numerically identical, so no conversion is needed. Some laboratories report mIU/L, which is 1000 times the mIU/mL value.
Why is there no ng/mL conversion for EPO?
Erythropoietin is standardised against a WHO biological reference preparation and reported in units of activity, not mass. Glycosylation varies between molecules, so activity and mass are not proportional and a molar factor would be misleading.
What does a low EPO with a high haematocrit mean?
It is the characteristic pattern of polycythaemia vera, where marrow proliferation is autonomous and suppresses endogenous erythropoietin. It warrants JAK2 V617F testing.
Related calculators
References
- WHO International Standard for Erythropoietin, recombinant, for bioassay.
- Arber DA et al. WHO classification of myeloid neoplasms. Blood.