Hematocrit: what it means

Also known as: Hct, packed cell volume

Hematocrit is the percentage of your blood volume made up of red blood cells; it tracks closely with hemoglobin and shifts with hydration.

What it measures

Hematocrit is the fraction of your blood, by volume, that consists of red blood cells. It moves in step with hemoglobin and is interpreted together with it, so the two are almost always read side by side on a CBC.

Typical range

Often roughly 41–50% for men and 36–44% for women, with meaningful variation by lab, age, and altitude.

Reference ranges differ between labs and are printed on your own report — always read your result against that range, not a general one.

What a high result can mean

Dehydration
High altitude or smoking
Overproduction of red blood cells (e.g. polycythemia)

A high value is a starting point for a conversation, not a diagnosis — many causes are benign or temporary.

What a low result can mean

Anemia from any cause
Blood loss
Overhydration

Why the trend matters

Because hematocrit is sensitive to hydration, one reading can mislead — the trend across draws separates a true change in red-cell mass from a day you happened to be dehydrated.

When to talk to your doctor

Discuss a persistently high or low hematocrit with your doctor, especially if hemoglobin is also out of range.

This page is general education about a common lab test — it isn’t medical advice and can’t interpret your specific result. What a value means depends on your history, symptoms, and the rest of your labs, which is a conversation for you and your clinician.