Red Cell Distribution Width, or RDW, is a measurement included in a complete blood count (CBC), a routine blood test. It offers insights into the characteristics of your red blood cells. Understanding what an RDW of 14.5% signifies can help illuminate aspects of your overall health and potential underlying conditions.
What RDW Measures
RDW quantifies the variation in the size and volume of your red blood cells, a phenomenon known as anisocytosis. Red blood cells are typically uniform in size, generally ranging from 6.2 to 8.2 micrometers in diameter. A notable difference in their sizes suggests the body may be experiencing difficulties in producing healthy red blood cells. This measurement is expressed as a percentage, reflecting the spread of red blood cell sizes within a sample.
RDW provides information beyond just the total number of red blood cells. It offers a more nuanced view of red blood cell health by indicating how consistently your body is producing these oxygen-carrying cells. A higher RDW suggests a wider range of red blood cell sizes, meaning some cells are larger or smaller than others. Conversely, a lower RDW indicates that red blood cells are more uniform in size.
Interpreting an RDW of 14.5%
The reference range for RDW is typically between 11.5% and 14.5%. Some medical professionals consider an RDW above 14.5% to be elevated. Therefore, an RDW of 14.5% is at the upper limit of the normal range or may be considered borderline high.
If your RDW is 14.5%, it suggests a slight, but not necessarily concerning, variation in the size of your red blood cells. This could simply represent normal biological variation. However, being at the upper end of the normal range or borderline high might also serve as an early indicator of subtle changes in red blood cell production. Slight deviations near the upper limit of normal are common and do not automatically signal a serious health issue when considered in isolation.
Common Causes of Elevated RDW
An elevated RDW, even if borderline at 14.5%, can point to several underlying conditions that affect red blood cell production. One common cause is iron deficiency anemia, where the body produces smaller red blood cells alongside normal-sized ones due to insufficient iron. This deficiency leads to a wider range of cell sizes, increasing the RDW.
Deficiencies in vitamin B12 or folate can also lead to an elevated RDW. These deficiencies result in macrocytic anemia, where red blood cells become larger than average, contributing to greater size variation. Hemolytic anemias, where red blood cells are destroyed faster than they can be produced, can also cause an elevated RDW as the bone marrow releases immature cells of varying sizes.
Other conditions that may lead to a higher RDW include chronic diseases such as kidney disease, liver disease, and heart disease, as well as diabetes and certain cancers, like colorectal cancer. Recent blood loss or transfusions can also temporarily affect RDW levels. Thalassemia, an inherited blood disorder, can also cause RDW elevation.
Next Steps After an RDW Result
Receiving an RDW result, especially one at 14.5%, necessitates consultation with a healthcare provider for a comprehensive evaluation. RDW is one component of a complete blood count (CBC) and should not be interpreted in isolation. The full picture of red blood cell health emerges when RDW is considered alongside other parameters such as mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), and hemoglobin levels.
Your healthcare provider will assess your RDW in the context of your overall health, any symptoms you might be experiencing, and your medical history. For instance, a high RDW combined with a low MCV might suggest iron deficiency, while a high RDW with a high MCV could indicate vitamin B12 or folate deficiency. Depending on the complete CBC results and clinical findings, further diagnostic tests may be recommended to pinpoint any abnormal or borderline results.