# Haematocrit

Source: https://onco.cc/terms/haematocrit/  
OnCo record `haematocrit` (Term). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

The share of blood volume made up of red cells. Normal is roughly 40 to 50 percent; in polycythaemia vera treatment aims to keep it under 45 percent, because above that clots become much more likely.

## Summary

Haematocrit is measured on every full blood count. In polycythaemia vera it is the number treatment is steered by: the CYTO-PV trial showed that a target below 45 percent, compared with 45 to 50 percent, cut cardiovascular deaths and major clots by about two thirds. Some experts use a lower target of 42 percent in women, whose normal range is lower.

## Fields

- Kind: Term
- Last checked: 2026-09-16
- Tags: polycythaemia-vera; mpn

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/Hematocrit
- Wikipedia: https://en.wikipedia.org/wiki/Hematocrit

## Connected records

- cancers: [Polycythaemia vera (PV)](https://onco.cc/cancers/polycythaemia-vera/)
- trials: [CYTO-PV](https://onco.cc/trials/cyto-pv/)

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JSON: https://onco.cc/api/v1/entities/haematocrit.json