Red Cell Distribution Width (RDW) measures the variation in the size and volume of your red blood cells. This measurement is a standard part of a Complete Blood Count (CBC) test, frequently ordered by doctors to assess overall health. RDW helps healthcare providers understand the uniformity of these oxygen-carrying cells within your bloodstream.
Understanding RDW Values
The normal range for RDW values in adults is typically between 12% and 15%. An RDW result of 16% indicates an elevated value, signaling a greater-than-normal variation in red blood cell size. This means some red blood cells may be notably smaller, while others are larger than average. This condition, where red blood cells show significant size variation, is medically termed anisocytosis.
Imagine red blood cells as beads. Normally, they are uniform in size. An RDW of 16% means your ‘bead collection’ has a mix of very small, medium, and unusually large beads. This inconsistency can arise from processes affecting red blood cell production and lifespan.
Potential Causes of an Elevated RDW
An elevated RDW, such as a reading of 16%, often points towards conditions affecting red blood cell production or survival. Nutrient deficiencies are a common cause, as the body requires specific vitamins and minerals to produce healthy, uniformly sized red blood cells. For instance, iron deficiency leads to the production of smaller, paler red blood cells (microcytes) alongside normal or larger cells, increasing RDW.
Similarly, deficiencies in vitamin B12 or folate can also cause an elevated RDW. These vitamins are necessary for proper red blood cell maturation. When deficient, the bone marrow may release abnormally large, immature red blood cells (macrocytes) into the bloodstream, contributing to size variation. Addressing these nutrient shortfalls often helps normalize RDW values.
Beyond nutrient deficiencies, other types of anemia are frequently associated with a high RDW. Anemias caused by chronic diseases, such as kidney disease or inflammatory conditions, can also result in an elevated RDW due to impaired red blood cell production.
Other less common causes for an elevated RDW include certain liver diseases, which can affect red blood cell shape and size, and recent blood transfusions. After a transfusion, the presence of donor cells alongside the recipient’s own cells can temporarily increase RDW. Bone marrow disorders, though less frequent, might also manifest with a high RDW due to abnormal red blood cell development.
The Role of Other Blood Test Results
An RDW value is rarely interpreted in isolation. Doctors analyze it alongside other values from the Complete Blood Count, particularly the Mean Corpuscular Volume (MCV), which measures the average size of your red blood cells. The interplay between RDW and MCV provides specific clues about the potential underlying cause of an elevated RDW.
For example, a high RDW combined with a low MCV often suggests iron deficiency anemia, where the average red blood cell size is small but cell sizes vary significantly. Conversely, a high RDW paired with a high MCV frequently points towards vitamin B12 or folate deficiency, where the average red blood cell size is large but cells still vary greatly.
A high RDW with a normal MCV can occur in the early stages of iron deficiency anemia or in certain conditions like sickle cell disease or thalassemia trait. These combined readings help physicians narrow down possibilities, guiding them towards further diagnostic steps. The RDW indicates red blood cell heterogeneity, which, when considered with other parameters, aids in differentiating various blood disorders.
Next Steps and Medical Consultation
An RDW of 16% is a clinical finding that requires interpretation within the full context of your health. It is not a standalone diagnosis, and understanding its implications requires professional medical assessment. Your healthcare provider will consider this result alongside your complete medical history, any symptoms you might be experiencing, and other values from your Complete Blood Count.
The doctor who ordered the test is best equipped to explain what your specific RDW result means for you. They may recommend further diagnostic tests, such as iron studies or vitamin B12 and folate levels, to pinpoint the exact cause of the elevated RDW. Based on the findings, follow-up actions could involve dietary adjustments, vitamin supplementation, or other targeted treatments for an identified underlying condition. Always avoid self-diagnosis or initiating any supplements without explicit guidance from a qualified medical professional.