RBC; erythrocyte count; red count
To evaluate any change in the number of red blood cells in your blood
As part of a full blood count (FBC), which may be requested for a variety of reasons
A blood sample drawn from a vein in your arm or by a finger-prick (children and adults) or heel-prick (newborns)
This test counts the number of red blood cells (RBC) in a litre of blood. Red blood cells, which are made in the bone marrow, carry oxygen from the lungs to the cells and transport carbon dioxide from the cells to the lungs. Women tend to have lower RBC counts than men, and levels tend to decrease with age. Changes in RBC are usually associated with changes in haemoglobin levels. When the values of the RBC and haemoglobin decrease by more than 10 per cent of the expected normal value, the patient is said to be anaemic. When the values increase above this range, the patient is said to be polycythaemic.
The test is performed on a blood sample taken by a needle placed in a vein in the arm or by a finger-prick (for children and adults) or heel-prick (for newborns).
A RBC count is used to evaluate any type of decrease in red blood cells (anaemia) or increase in red blood cells (polycythaemia) as measured per litre of blood. These changes must be intterpreted in conjunction with other parameters, such as haemoglobin, haematocrit and/or RBC indices
A RBC count is normally requested as a part of the full blood count (FBC) often as part of a routine examination, pre-surgical procedure or for other clinical reasons. The test is also repeated in patients who have haematological disorders, bleeding problems, chronic anaemias, polycythaemia and/or in patients undergoing chemotherapy or radiation treatment.
A low RBC count may indicate anaemia, bleeding, kidney disease, bone marrow failure (for instance, from radiation or a tumour), malnutrition, or other causes. A low count may also indicate nutritional deficiencies of iron, folate, vitamin B12, and vitamin B6. A decreased number of RBCs results from either acute or chronic blood loss. Acute blood loss is a rapid depletion of blood volume. Chronic blood loss stems from various conditions that often results in some form of an anamia. Chronic anaemias are due to loss of small amounts of blood over a long period of time (bleeding), mechanical destruction of the RBCs, or some physiological problem such as decreased RBC production.
A high RBC count may indicate congenital heart disease, dehydration, obstructive lung disease, bone marrow over-production or situations involving tissue hypoxia.
The list below includes some of these conditions.
Alteration of the number of RBCs is often transient and can be easily corrected and/or returned to normal levels by eliminating the causative agent. Normal decreases in red blood cells are seen during pregnancy as a result of normal body fluid increases that dilute them.
Living at high altitudes causes an increase in RBC counts; this is your body's response to the decreased oxygen available at these heights.
Drugs that may increase RBC levels include gentamicin and methyldopa.
Full blood count (FBC), blood film
RCPA Manual - Red cell count
Last Review Date: December 1, 2016