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Also known as: Packed cell volume; PCV; Hct
Related tests: Full blood count

At a Glance

Why Get Tested?

If your doctor suspects that you have anaemia (too few red blood cells), polycythaemia (too many red blood cells), or dehydration

When to Get Tested?

As part of a full blood count (FBC), which may be requested for a variety of reasons

Sample Required?

A blood sample drawn from a vein in your arm or by a finger-prick (children and adults) or heel-prick (newborns)

Test Preparation Needed?


The Test Sample

What is being tested?

Blood is a mixture of cells and plasma. The haematocrit (Hct or PCV) is a measurement of the proportion of blood that is made up of cells. The value is expressed as a fraction of cells in blood. For example, a Hct of 0.40 means that there are 40 millilitres of cells in 100 millilitres of blood.

The haematocrit rises when the number of red blood cells increases or when the blood volume is reduced, as in dehydration. The falls to less than normal, indicating anaemia, when your body decreases its production of red blood cells or increases its destruction of red blood cells.

How is the sample collected for testing?

A sample is obtained by drawing blood through a needle placed in a vein in the arm or by a finger-prick (for children and adults) or a heel-prick (for newborns).

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed.

The Test

Common Questions

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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.