High red blood cell count
What causes a high red blood cell count?
- Mary / California
Mayo Clinic hematologist Ruben Mesa, M.D., and colleagues answer select questions from readers.
Answer
A normal red blood cell count ranges from 4.7 to 6.1 million cells per microliter (mcl) in males and 4.2 to 5.4 million cells per mcl in females. A high red blood cell count usually suggests that you have too many red blood cells. Although a high red blood cell count is not a specific disease, it may be a sign of an underlying problem. Causes include:
- Living at a high altitude
- Smoking
- Congenital heart disease
- Failure of the right side of the heart (cor pulmonale)
- Scarring and thickening of the lung tissue (pulmonary fibrosis)
- A rare bone marrow disorder (polycythemia vera)
- Dehydration, such as from severe diarrhea or excessive sweating
- Kidney disease
- Exposure to carbon monoxide
- Anabolic steroid use
In severe cases, a high red blood cell count can impair circulation and lead to abnormal clotting. Treatment of a high red blood cell count is directed at the underlying cause.


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