Routine blood tests offer valuable insights into an individual’s health. One such measurement, frequently included in a complete blood count (CBC), is the Red Cell Distribution Width, or RDW.
Understanding Red Cell Distribution Width (RDW)
RDW, or Red Cell Distribution Width, quantifies the variation in the size of your red blood cells (erythrocytes). This test is a standard part of a complete blood count (CBC) and assesses the uniformity of these cells. Imagine a basket of apples: if all the apples are roughly the same size, RDW is low. If there’s a mix of very small and very large apples, RDW is high. The RDW value, expressed as a percentage, reflects this variation in cell size, not their average size.
Interpreting Your RDW Values
For adults, a normal RDW range is typically 11.5% to 14.5%, though this can vary by laboratory. A “high RDW” indicates a greater variation in red blood cell size, a condition medically termed anisocytosis. This means that cells are not uniform in size; some are larger or smaller than average. A “low RDW” signifies that the red blood cells are very uniform in size. This result is generally considered favorable and is not typically associated with specific blood disorders. When medical issues are present, the RDW is usually elevated, rather than low.
Conditions Linked to RDW Variations
An elevated RDW often suggests issues affecting red blood cell production or destruction. Various types of anemia are commonly associated with a high RDW. For instance, iron deficiency anemia can cause a high RDW because the body produces smaller red blood cells due to insufficient iron, while existing normal-sized cells may still be present, leading to a mix of cell sizes. Similarly, deficiencies in vitamin B12 or folate can also result in a high RDW, as these deficiencies impair red blood cell maturation, leading to the production of unusually large cells alongside normal ones. Conditions that cause the destruction of red blood cells, such as hemolytic anemias, can also lead to an increased RDW as the bone marrow tries to compensate by releasing new, often varying-sized, cells.
Beyond anemias, elevated RDW values have been linked to other health concerns. These include chronic conditions like kidney disease, liver disease, diabetes, and inflammatory conditions. Some studies also suggest a connection between high RDW and cardiovascular diseases or certain cancers, such as colorectal cancer.
The Role of RDW in Your Overall Health Picture
RDW is one piece of a larger diagnostic puzzle and is rarely interpreted in isolation. Healthcare professionals typically analyze RDW results in conjunction with other red blood cell indices, such as Mean Corpuscular Volume (MCV), Mean Corpuscular Hemoglobin (MCH), and Mean Corpuscular Hemoglobin Concentration (MCHC), which are also part of the complete blood count. For example, a high RDW combined with a low MCV can point towards iron deficiency anemia, while a high RDW with a high MCV might indicate a vitamin B12 or folate deficiency.
A doctor considers RDW alongside a patient’s symptoms, medical history, and other laboratory findings to form a comprehensive understanding of their health status. An abnormal RDW might prompt further diagnostic investigation to identify the root cause. An elevated RDW does not automatically signify a serious condition, but rather serves as an indicator that warrants further medical evaluation. Consulting a healthcare professional for accurate interpretation and to discuss any concerns is always the recommended course of action.