What is RDW in a blood test

An examination of RDW is usually performed as part of a complete blood count. Save Getty Images

If your doctor has diagnosed you a type of anemia or iron deficiency, then at some point you must have had a blood test that reflects an abnormal count RDW. RDW levels, along with a combination of some other important blood counts are those that help your doctor find out what type of anemia you have and why has appeared. Health Plan of New York HIP explains that there are more than 400 known types of anemia, which can in turn subdivided into subgroups related to blood loss, low red blood cell production and the disappearance of red blood cells .

What RDW means?

RDW is short for "distribution width of red blood cells" (Red blood cell distribution width). According to the online testing laboratory, RDW calculates the different sizes of red blood cells (RBC, for its acronym in English) in a blood sample volume. A RDW test is usually done as part of a complete blood count or complete blood cell counts.


It is virtually impossible to discuss the appearance of a blood RDW excluding MCV or mean corpuscle. The MCV goes hand in hand with a broad red blood cell distribution (RDW) in terms of anemia and other blood disorders and the values ​​of both are influenced by the other. For example, low levels of MCV in combination with normal RDW can indicate chronic illness, while RDW MCV low combined with low may indicate iron deficiency. Similarly, a normal reading of MCV in combination with a normal RDW may represent a chronic disorder and normal MCV combined with high RDW can mean a vitamin B12 deficiency. Chronolab.com also reveals that when levels are elevated MCV and RDW is normal, pre-leukemia may be present. Both MCV and RDW high high can mean that a patient experiences folate deficiency.

RDW calculation

The RDW is calculated by dividing the standard deviation (SD for short English) by the mean corpuscular volume (MCV) and multiplying by 100. The standard deviation represents the volume of erythrocytes or red blood cells that are in the smear the blood. According Beckman Coulter, the equation for calculation is RDW RDW = SD / MCV x 100.

Normal reference range for blood tests RDW

Normal RDW are between 11 and 14 percent, with a range of RDW optimum value of 13 percent. When the RDW values ​​rise above normal levels, suspected of several disorders. According to the journal Archives of Internal Medicine, counts RDW may also play an important role in predicting mortality, especially in patients with cardiovascular disease and cancer. In fact, patients who give more normal reference range in a test of RDW may suffer more health risks than those patients whose values ​​are lower RDW.


Anisocytosis RDW is diagnosed when levels in blood tests indicate excessively high values ​​of red blood cells in the form of variable. In the book "Diagnostic Hematology"The author Norman Beck explains that the presence of anisocitosis in a diagnostic blood test is so common that it is often dismissed as a component in making the assessment. However, advances in medicine have shed new light on the importance of anisocitosis during patient assessment. When measured against other anisocitosis blood cell values, high values ​​of RBC can help make a better determination of the type of anemia in a patient.

Consult your health care provider

Blood tests and their results are a part of general diagnostic image and are not intended to be the only tool that can be used for diagnosis or prognosis of the disease. Call your doctor for a complete physical examination and an assessment of symptoms is the best method for understanding the results of the blood test.