Red Cell Distribution Width (RDW) is a parameter in a standard complete blood count (CBC) that measures the variation in the size of your red blood cells. Understanding what a low RDW result indicates is an important part of interpreting your overall health. This article explains the meaning of a low RDW result and its potential implications, emphasizing it is just one piece of a larger diagnostic puzzle.
What RDW Measures and What a Low Result Suggests
RDW quantifies the variation in the volume and size of red blood cells in a blood sample. Healthy red blood cells are relatively uniform in size, typically ranging from 6.2 to 8.2 micrometers. The RDW test assesses this uniformity. A normal RDW range generally falls between 11.5% and 14.5%, though values can vary by lab.
A low RDW result indicates that your red blood cells are very similar in size, showing little variation. This suggests consistent red blood cell production. While a high RDW indicates significant variation, a low RDW is less common and generally not a cause for concern on its own.
Common Conditions Linked to Low RDW
A low RDW is rarely a standalone diagnostic marker and is always considered with other red blood cell parameters, such as Mean Corpuscular Volume (MCV), Mean Corpuscular Hemoglobin (MCH), and Mean Corpuscular Hemoglobin Concentration (MCHC). When red blood cells are uniformly small (microcytosis) and RDW is low, it can point towards specific conditions. One is thalassemia minor, a genetic blood disorder where red blood cells are consistently smaller than average but maintain a very uniform size.
Some types of anemia of chronic disease can also present with a low RDW, particularly if the red blood cells are uniformly microcytic or normocytic. In these cases, the body’s inflammatory response can affect red blood cell production in a way that leads to a consistent cell size. Additionally, a low RDW might be observed after recent blood transfusions, as donor cells can temporarily homogenize the red blood cell population. Some healthy individuals naturally have a low RDW without any underlying medical condition.
Guidance After a Low RDW Result
A low RDW result typically does not warrant immediate alarm, especially if it is the only abnormal finding. Always discuss your results with your healthcare provider. They will interpret the RDW value in the context of your complete blood count, medical history, and any symptoms.
Your doctor may decide no further action is necessary if other blood parameters are normal and you are asymptomatic. If there are other abnormal findings or clinical concerns, additional tests might be recommended. The RDW test provides valuable information, but it is one component among many for a comprehensive understanding of your health.