A hematocrit test is part of a complete blood count (CBC). The proportion of red blood cells compared with all blood cells may help your doctor make a diagnosis or monitor your response to a treatment.

A lower than normal hematocrit may indicate:

  • An insufficient supply of healthy red blood cells (anemia)
  • A large number of white blood cells — usually a very small portion of your blood — due to long-term illness, infection, leukemia, lymphoma or other disorders of white blood cells
  • Vitamin or mineral deficiencies
  • Recent or long-term blood loss

A higher than normal hematocrit may indicate:

  • Dehydration
  • A disorder, such as polycythemia vera, that causes your body to produce too many red blood cells
  • Lung or heart disease — if the body senses low oxygen levels, it will make more red blood cells in an effort to increase the amount of oxygen in the blood
Jul. 10, 2013