High red blood cell count
DEFINITION
A high red blood cell count indicates there are too many red blood cells circulating in your bloodstream. Red blood cells (RBCs), also called erythrocytes, are produced in your bone marrow and transport oxygen from your lungs to tissues throughout your body. A high red blood cell count is also called erythrocytosis (uh-rith-roh-sie-TOE-sis).
The threshold for a high red blood cell count is somewhat different from one medical practice to another. A high red blood cell count is generally defined as more than 5.72 million red blood cells per microliter (mcL) of blood for men and 5.03 million per mcL for women. In children, the threshold for high red blood cell count varies with age and sex.
CAUSES
A high RBC count may occur because:
- Red blood cell production increases to compensate for low oxygen levels due to poor heart or lung function
- Red blood cell production increases to compensate for lower oxygen levels at higher altitudes
- The kidneys release too much of a protein (erythropoietin, or EPO) that enhances red blood cell production
- The bone marrow is producing too many red blood cells
- The oxygen-carrying capacity of red blood cells is reduced
- The loss of blood plasma (the liquid component of blood), often due to sodium and water depletion, results in the appearance of higher levels of red blood cells
Specific causes of high red blood cell count may include:
- Anabolic steroids, which stimulate red blood cell production
- Carbon monoxide poisoning
- Congenital heart disease in adults
- COPD
- Dehydration
- EPO doping (injections of erythropoietin (EPO) to enhance athletic performance)
- Heart failure
- Hemoglobinopathies (conditions present at birth that impair the oxygen-carrying capacity of red blood cells)
- Kidney cancer
- Kidney transplant
- Living at a high altitude, where there’s less oxygen in the air
- Other types of heart disease
- Other types of lung disease
- Polycythemia vera
- Pulmonary fibrosis
- Sleep apnea
- Smoking, which may result in low blood oxygen levels
WHEN TO SEE A DOCTOR
A high red blood cell count is rarely an unexpected finding or simply discovered by chance. It’s usually found when your doctor has ordered tests to help diagnose a condition you have. Talk to your doctor about what these results mean. A high red blood cell count and results from other tests may indicate the cause of your illness, or your doctor may suggest additional tests to monitor your condition.