High red blood cell counts can be caused by dehydration, smoking, living at high altitude, lung or heart disease, or a bone marrow condition. A doctor can find the cause.
Normal range
About 4.35 to 5.65 million cells per microliter for men and 3.92 to 5.13 for women.
Causes of high count (erythrocytosis)
- Dehydration.
- Smoking.
- Living at high altitude.
- Lung or heart disease.
- Sleep apnea.
- Polycythemia vera, a bone marrow disorder.
- Testosterone or EPO use.
What to do
See a doctor to find the cause and check hemoglobin and hematocrit.
Normal range
Typical red blood cell counts are about 4.7 to 6.1 million cells per microliter for men and 4.2 to 5.4 million for women. Hemoglobin and hematocrit are also checked. Ranges vary by lab, altitude and age.
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Causes of a high count
- Dehydration, which concentrates blood.
- Living at high altitude, where the body makes more red cells.
- Smoking and carbon monoxide exposure.
- Chronic lung disease (COPD), sleep apnea and other conditions that lower oxygen.
- Heart disease, especially congenital heart disease.
- Kidney tumors or cysts that make erythropoietin (EPO).
- Testosterone therapy and anabolic steroids.
- EPO use or blood doping.
- Polycythemia vera, a bone marrow disorder with a JAK2 gene mutation, found in about 2 per 100,000 people per year.
Symptoms
Headache, dizziness, itching after a warm shower, redness of the face, fatigue, blurred vision and a high risk of blood clots.
Why it matters
Thick blood raises the risk of clots, stroke and heart attack.
What to do
A doctor will repeat the test, review medications and health conditions and may check oxygen levels, EPO and JAK2 testing. Treatment depends on the cause: stopping smoking, treating sleep apnea, adjusting testosterone, hydration, or therapeutic phlebotomy (removal of blood) and aspirin for polycythemia vera. Medicines such as hydroxyurea or ruxolitinib are options for some.
Prevention
Drink enough water, avoid smoking and follow up on abnormal blood tests.
See a doctor
Do not self treat, since lowering red blood cells without cause can be dangerous.
Reference ranges and causes
Typical red blood cell counts are about 4.7 to 6.1 million cells per microliter for adult men and 4.2 to 5.4 million for adult women, though laboratory ranges differ. A high count is called erythrocytosis. Common secondary causes include dehydration, smoking, living at high altitude, chronic lung disease, sleep apnea and testosterone therapy, all of which raise oxygen demand or erythropoietin levels. Polycythemia vera is a rare blood cancer, affecting roughly 2 per 100,000 people a year, in which the marrow makes too many cells, and most cases carry a mutation in the JAK2 gene.
Why it matters and management
Thick blood raises the risk of clots, stroke and heart attack. Symptoms can include headache, dizziness, itching after a warm shower, flushed skin and fatigue. Tests may include hematocrit, oxygen levels, JAK2 testing and erythropoietin levels. Treatment depends on the cause: stopping smoking, treating sleep apnea, adjusting testosterone doses and staying hydrated can help. Polycythemia vera is treated with phlebotomy (drawing blood), low dose aspirin and sometimes medicines. See a doctor for persistently high counts or symptoms.
Based on data from the Mayo Clinic and the Leukemia and Lymphoma Society
