Red blood count

A red blood cell count can be used to measure a decrease in the number of red blood cells (anaemia) or an increase(polycythaemia).



An increase in red blood cells is known as polycythaemia and a decrease is known as [anaemia](/health-library/conditions/anaemia-iron-deficiency).

A red blood cell (RBC) count is usually carried out as part of a full blood cell (FBC) count, and can help diagnose health conditions that affect the blood.

For example, if you have a high red blood cell count it could be due to a condition such as [congenital heart disease](/health-library/conditions/congenital-heart-disease) or [dehydration](/health-library/conditions/dehydration).

A low red blood cell count may be a sign that you have anaemia, internal bleeding, [kidney disease](/health-library/conditions/kidney-disease-chronic) or [malnutrition](/health-library/conditions/malnutrition) (when a person’s diet does not contain enough nutrients to meet their body's demands).

A low count may also be a sign of an iron deficiency or a vitamin B6, [B12 or folate deficiency](/health-library/conditions/vitamin-b12-and-folate-deficiency/#introduction).


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Article information

A red blood cell count can be used to measure an increase or decrease in the number of red blood cells.