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Blood and lab tests

What Is Hematocrit on a Blood Test?

Hematocrit · say it: hee-MAT-oh-kritAlso written: Hct, HCT, packed cell volume, PCV, haematocrit

Short answer

Hematocrit is the share of your blood volume made up of red blood cells, shown as a percentage or a fraction on a blood count.

What it means

Blood is made of cells floating in a liquid called plasma. If you spun a tube of blood, the red cells would settle at the bottom. Hematocrit is how much of the tube those red cells take up.

It usually moves in the same direction as hemoglobin. A low hematocrit can go with anaemia, while a high one can be seen with dehydration, smoking, living at altitude or conditions where the body makes too many red cells.

Because hydration changes the amount of plasma, hematocrit can shift even when the number of red cells has not. Doctors read it together with hemoglobin and the other parts of the blood count.

Where you may see it

  • Complete blood count (CBC)
  • Pre-surgery blood tests
  • Dehydration and blood donation checks

📄 How it looks on a report

Hematocrit 0.36 L/L L

🙅 What it does not mean

  • A high hematocrit does not always mean too many red cells; being dehydrated can raise it.
  • It does not explain the cause of a change; other tests are needed for that.
  • It is not a separate problem from hemoglobin; the two usually tell a similar story.

🗒️ Questions to ask your doctor

🧾 Reports where you will see “Hematocrit”

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💊 Medicines whose labels mention “Hematocrit”

Plain-English explanations of each medicine, from its official FDA label.

  • Primaquine

    An antimalarial medicine of the 8-aminoquinoline group, as described in the label

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🧩 Related words

HemoglobinMCV (Mean Corpuscular Volume)Reference RangeHigh and Low Flags (H and L)

🔎 Look up another word

More words: blood and lab tests

ALT (Alanine Aminotransferase)AST (Aspartate Aminotransferase)BilirubinCreatinineCRP (C-Reactive Protein)Culture and SensitivityeGFR (Estimated Glomerular Filtration Rate)ElectrolytesESR (Erythrocyte Sedimentation Rate)Fasting SampleFerritinHbA1cAll medical words →
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