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Explain the tests: Complete blood count (CBC) – High red cell count (Part 3)

A number of conditions can cause high red blood cell count.  This is called polycythemia.  Red cells are responsible for bringing oxygen from the lungs to the tissues. If the blood is getting less oxygen than normal, the bone marrow will produce more red cells to compensate.  Excessive release of erythropoietin, a molecule that triggers red cell production, can also cause high red blood cell count.  Additionally, changes in amount of fluid in the blood stream can artificially alter red blood cell and hemoglobin levels.

Normal range for red blood count:

  • Adult women: 3.9-5.0 million cells/µL
  • Adult men: 4.3-5.7 million cells/µL

Reasons for making too many red blood cells:

  • High levels of erythropoietin, a molecule that tells the bone marrow to make red cells
  • Lower levels of oxygen in blood stream
  • Neoplastic conditions
  • Relative polycythemia, in which reduction of blood volume causes an artificial increase in red blood cells

Some conditions that cause lower oxygenation of the blood, triggering polycythemia:

  • Lung diseases, such as COPD, sleep apnea and pulmonary fibrosis.
  • Heart conditions, such as congestive heart failure.
  • Carbon monoxide poisoning.
  • Hemoglobin defects, such as 2,3-BPG deficiency, which causes hemoglobin to hold onto oxygen too tightly.
  • Lengthy stays at high altitude.

Some conditions that cause elevated erythropoietin:

  • Poor blood flow to the kidney, such as in narrowing of the renal artery, hydronephrosis and kidney cysts. The body interprets as low oxygenation.
  • Chuvash polycythemia, which causes overactivity of the erythropoietin gene.

Some neoplastic conditions that cause excessive proliferation of red cells:

  • Polycythemia vera. This myeloproliferative disorder (MPN) is strongly associated with the JAK2 V617F mutation.
  • Cancers such as renal cell carcinoma and adenocarcinoma.

Situations that cause artificially high red blood cell count:

  • Hypovolemia, from dehydration, alcoholism, obesity, smoking or third spacing.
  • Use of some diuretics.

Some medications that cause secondary polycythemia:

  • Anabolic steroids
  • Testosterone


Special notes on high red cell count for mast cell patients:

  • Polycythemia vera is a myeloproliferative neoplasm like systemic mastocytosis. It is a common comorbidity for patients with SM-AHNMD.  Some SM patients are positive for the JAK2 V617F mutation without having polycythemia vera.
  • Third spacing (fluid from the blood stream becoming trapped in the tissues) occurs in many mast cell patients as a regular symptom, as well as during anaphylaxis. This can cause the red cell count to appear artificially high.