====== Red blood cell distribution width ======
The [[red blood cell]] distribution width (RDW) is a parameter used in [[blood test]] to evaluate the size and variability of red blood cells (erythrocytes). RDW is expressed as a percentage or as a numerical value, and represents the amplitude of the distribution of erythrocyte sizes in a blood sample.

RDW is used along with other blood parameters, such as [[mean corpuscular volume]] (MCV) and mean corpuscular hemoglobin (MCH), to evaluate the presence of anemia and to aid in the diagnosis and monitoring of diseases related to red blood cells.

A high RDW indicates greater variability in the size of erythrocytes, which may be indicative of anemia caused by iron deficiency, chronic inflammation, or kidney disease. On the other hand, a low RDW indicates less variability in the size of erythrocytes, which may be indicative of anemia caused by vitamin B12 or folic acid deficiency, or a liver disease.

It is important to note that RDW is not a diagnosis in itself and should be evaluated in conjunction with other blood parameters and the patient's medical history.