RDW-CV (Red Cell Distribution Width) in %

Complete Blood Count (CBC)

A healthy result should fall into the range 11.7 - 15 %.

Red blood cell distribution width is a measure of the average size of the red blood cells. Red blood cells are important because they transport hemoglobin, which transports oxygen throughout the body. Assessment of red blood cells is typically done in a comprehensive blood count (CBC), which also measures features of white blood cells and platelets. The CBC is a very common test. A healthcare professional may order a CBC as a part of a routine health examination or when a person has signs and symptoms that may be related to disorders that affect blood cells, such as:





If someone has been diagnosed with a disease that is known to affect blood cells, a CBC will be ordered regularly to monitor the condition. Similarly, if someone is receiving treatment for a blood-related disorder, a CBC will be ordered regularly to determine if the treatment is effective. Further, some therapies (e.g., chemotherapy) can affect production of blood cells and some medications can decrease counts overall. In these cases, a CBC can be used to monitor these drug treatments.

Specifically, red blood cell indices (which include mean cell volume, hemoglobin count per red blood cell, and hemoglobin count relative to cell size) are used to diagnose the cause and severity of anemia, a condition characterized by too few red blood cells.

Classification of Anemia:

Type of anemia

Mean cell volume

Macrocytic anemia

RDW above normal

Normocytic anemia

RDW normal

Microcytic anemia

RDW below normal

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What does it mean if your RDW-CV (Red Cell Distribution Width) in % result is too low?

A low RDW means that the red blood cells vary little in size.  Although a normal or low RDW score isn’t typically problematic (as it simply indicates that, on average, the red blood cells have a uniform size), it can indicate macrocytic anemia or microcytic anemia. In these two disorders the red blood cells do not vary much in size because they are either all small or all large.

What does it mean if your RDW-CV (Red Cell Distribution Width) in % result is too high?

An abnormally high RDW indicates mixed populations of small and large RBCs, with younger RBCs tending to be larger. Deficiencies of vitamin B12 or folate can cause RDW to be elevated; although, a varied size distribution of red blood cells is a classic symptom of iron deficiency anemia. To further determine the cause of a high RDW level, a healthcare professional may compare the score to a patient’s mean corpuscular volume (MCV)—the average amount of space occupied by each red blood cell. If both the RDW and MCV are increased, then liver disease is a possibility.

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