A high red blood cell (RBC) count means there are more red blood cells in your blood than normal. Red blood cells carry oxygen from the lungs to the rest of the body, so having too many can make the blood thicker and potentially slow its flow, increasing the risk of blood clots. High RBC counts (also called erythrocytosis or polycythemia) can be caused by several factors or conditions, including:
- Low oxygen levels in the body, which can happen due to lung diseases, sleep apnea, or living at high altitudes.
- Heart conditions that affect oxygen circulation.
- Dehydration, which concentrates the blood.
- Smoking, which leads to increased red blood cell production to compensate for reduced oxygen.
- Kidney diseases or tumors that produce extra erythropoietin, a hormone that stimulates red blood cell production.
- Genetic conditions such as polycythemia vera, a bone marrow disorder causing excessive red blood cell production.
- Certain cancers and some lifestyle factors, including stress.
Symptoms of a high RBC count may include headache, dizziness, vision problems, fatigue, shortness of breath, and flushed skin, although some people may have no symptoms. A high red blood cell count is often found during routine blood tests and is a signal to investigate further for the underlying cause. If you have a high RBC count, it is important to consult your healthcare provider for additional tests and appropriate management to address the cause and reduce potential complications from thickened blood. Normal RBC count ranges generally vary by sex and age but are approximately 4.7 to 6.1 million cells per microliter for men, 4.2 to 5.4 million for women, and 4.0 to 5.5 million for children. In summary, a high red blood cell count means your blood has more erythrocytes than usual, which can impact blood flow and oxygen delivery, and may indicate an underlying condition needing medical attention. This explanation is based on information from medical sources including MedlinePlus, Cleveland Clinic, Mayo Clinic, and others.
