A RBC count, or red blood cell count, measures the number of red blood cells present in a given volume of blood. Red blood cells are the most common type of blood cell, responsible for both carrying oxygen from your lungs to every cell in your body as well as bringing back carbon dioxide to the lungs to be exhaled.
A RBC count is almost always part of a routine blood test known as complete blood count (CBC).
A normal RBC count indicates a normal amount of red blood cells in blood, meaning an effective oxygen transportation and circulatory system.
The purpose of the RBC count is to find out if the number of red blood cells you have is normal or abnormal. An RBC count may be included in routine blood testing during a medical check-up and is always included as part of a complete blood count measuring the number of red blood cells, white blood cells and platelets in addition to the amount of hemoglobin present in the red blood cells.
Measuring RBCs can help diagnose anemia, a condition in which the body doesn’t have enough healthy red blood cells. There are different types of anemias with distinct causes. A low RBC count is a key indicator of anemia, thus requiring additional tests can help determine its underlying cause.
RBC count may also be used to help diagnose other conditions that affect red blood cells, such as kidney problems, a type of white blood cell cancer, or bone marrow disorders.
A low RBC count, also known as anemia, means that there are not enough red blood cells in the blood. Furthermore, anemia may be caused by a variety of factors, including deficiency in iron, vitamin B12 or folate.
Blood loss, causing the total amount of red blood cells to decrease has an overall negative effect on RBC count. Conditions affecting the production of red blood cells may also cause a decreased RBC count. Such conditions include bone marrow disorders such as leukemia, aplastic anemia and myelodysplastic syndrome.
A high RBC count, also known as erythrocytosis or polycythemia, either indicates that the body is producing too many red blood cells, or that the red blood cells are circulating in a reduced blood volume due to dehydration.
Dehydration is the most common cause for elevated levels of red blood cells, and can be caused by insufficient fluid intake, diarrhea, vomiting or heavy sweating. Although this is not a “real” erythrocytosis, it is important to exclude conditions causing an overproduction of red blood cells, such as the bone marrow disorder polycytemia vera, kidney disease or hormonal imbalances such as testosterone excess.
Other underlying causes may be smoking and chronic hypoxia (often caused by chronic obstructive pulmonary disease (COPD) or high altitudes).
Having an elevated RBC count can increase the risk of blood clots, which is why it is important to have a healthcare professional interpreting the results with other clinical findings to understand its proper meaning.