Blood test results often contain unfamiliar terms, and “RBC distribution width high” is one such example. While some findings may seem concerning, a high red blood cell distribution width (RDW) is a common result that often indicates an underlying condition. Understanding this measurement helps clarify its significance.
What is Red Blood Cell Distribution Width?
Red Blood Cell Distribution Width (RDW) quantifies the variation in the size of your red blood cells. Normally, red blood cells are fairly uniform, typically ranging from 6 to 8 micrometers in diameter. A greater difference in cell size is known as anisocytosis, and this elevates your RDW.
RDW is routinely included in a complete blood count (CBC), a test detailing blood components like red blood cells, white blood cells, and platelets. A high RDW value indicates your red blood cells vary more in volume than typical. This variability occurs when both smaller and larger red blood cells are present.
Common Reasons for High RDW
Several medical conditions and factors can lead to an elevated RDW. One common cause is iron deficiency anemia, where insufficient iron leads to the production of smaller red blood cells alongside normal ones. As iron stores deplete, new red blood cells become progressively smaller, increasing size variation.
Deficiencies in vitamin B12 or folate can also result in a high RDW. These deficiencies lead to the production of abnormally large red blood cells, known as macrocytic anemia, which increases size variation. In cases of combined deficiencies, such as both iron and vitamin B12 deficiency, the RDW can be particularly high even if the average red blood cell size appears normal.
Other conditions causing elevated RDW include chronic diseases like kidney, liver, and heart disease, as well as chronic inflammatory conditions. Acute or chronic blood loss can also lead to a high RDW as the body replaces lost red blood cells, sometimes producing cells of varying sizes. Myelodysplastic syndromes, disorders where bone marrow doesn’t produce enough healthy blood cells, can also be associated with an elevated RDW.
Understanding Your High RDW Result
A high RDW result is not a standalone diagnosis; it serves as a clue for further investigation. Healthcare providers evaluate RDW alongside other complete blood count parameters, such as mean corpuscular volume (MCV) and hemoglobin levels. For instance, a high RDW combined with a low MCV (indicating smaller average red blood cell size) often suggests iron deficiency anemia. Conversely, a high RDW with a high MCV (indicating larger average red blood cell size) might point towards vitamin B12 or folate deficiency.
Even with a normal RDW, an underlying medical condition like certain types of anemia or chronic diseases could still be present. Therefore, consulting a healthcare professional is recommended for proper interpretation of your RDW result and overall clinical picture. Your doctor may recommend additional tests or treatments to determine the cause of the elevated RDW and address any underlying health concerns.