Hematocrit / Packed Cell Volume (HCT / PCV)

What it measures

Hematocrit is the percentage of total blood volume taken up by red blood cells, which carry oxygen. A low value means anemia. PCV and HCT are measured differently but look at the same thing. Cats and dogs have different ranges, so use the range on your report.

What a high value may mean

The most common cause is dehydration: there is less water in the blood, so red cells make up a larger share, not because there are truly more of them. Rarely, red cells really are increased (polycythemia), which can be linked to low oxygen or certain tumors.

What a low value may mean

It means anemia, with three main causes: blood loss, destruction of red cells (hemolysis), and too little production by the bone marrow. IV fluids diluting the blood and sedatives or anesthetics (which relax the spleen so it holds more red cells) can also lower the value temporarily.

Usually read together with

Reticulocytes (to see whether the bone marrow is making new red cells), red cell indices, and total protein; urea and creatinine as well when judging dehydration.

When to follow up

If your cat has pale gums, low energy, or faster breathing along with a low hematocrit, see the vet promptly. For a mild drop, your vet will look for the cause with other tests and plan follow-up.

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