Understanding Red Cell Distribution Width (RDW) and Its Reference Range
Learn about Red Cell Distribution Width (RDW), its normal range of 11.5–14.5%, and what these values indicate about your health.
Check your result
Calculated in your browser - the number is not sent anywhere.
On this page · 6
Red Cell Distribution Width (RDW) is a measurement that reflects the variation in size of your red blood cells. It is part of a standard complete blood count (CBC) test and can provide valuable insights into your overall health. Understanding RDW and its reference range can help you interpret your lab results and discuss any concerns with your healthcare provider.
What is RDW?
Red Cell Distribution Width (RDW) measures the range of variation in the size of your red blood cells. Red blood cells are responsible for carrying oxygen from your lungs to the rest of your body. Ideally, these cells should be uniform in size for optimal function. RDW is expressed as a percentage and is calculated by dividing the standard deviation of red blood cell volumes by the mean corpuscular volume (MCV) and multiplying by 100.
Check your own value in the calculator above
Why is RDW important?
RDW is an important marker because it helps identify potential health issues related to red blood cell production and destruction. A high RDW can indicate a greater variation in red blood cell size, which may suggest conditions such as anemia, nutrient deficiencies, or bone marrow disorders. Conversely, a normal RDW suggests that your red blood cells are relatively uniform in size, which is generally a sign of good health.
RDW reference range
The typical reference range for RDW in adults is 11.5–14.5%. This means that if your RDW falls within this range, your red blood cells are generally uniform in size. Values outside this range may warrant further investigation by your healthcare provider to determine the underlying cause.
Factors affecting RDW levels
Several factors can influence RDW levels. Nutritional deficiencies, such as a lack of iron, vitamin B12, or folate, can lead to increased RDW. Certain medical conditions, including anemia, liver disease, and bone marrow disorders, can also affect RDW. Additionally, recent blood loss or transfusions may temporarily alter RDW levels.
Frequently asked questions
What does a high RDW mean? A high RDW indicates a greater variation in the size of your red blood cells. This could be due to conditions like anemia, nutrient deficiencies, or other health issues that affect red blood cell production.
Can RDW be low? While RDW is typically discussed in terms of being high, a low RDW is uncommon and not usually a cause for concern. It generally means your red blood cells are uniform in size.
How is RDW measured? RDW is measured as part of a complete blood count (CBC) test. This test is commonly performed during routine health check-ups or when investigating specific health concerns.
Does RDW vary with age or gender? RDW values can vary slightly with age and between genders. However, the reference range of 11.5–14.5% applies broadly to adults, regardless of age or gender.
Can lifestyle changes affect RDW? Yes, lifestyle changes such as improving your diet to include sufficient iron, vitamin B12, and folate can help maintain normal RDW levels. Managing underlying health conditions can also stabilize RDW.
When to see a doctor
If your RDW falls outside the typical reference range of 11.5–14.5%, it is important to discuss the results with your healthcare provider. They can help determine if further testing or treatment is needed based on your overall health and any symptoms you may be experiencing.
Remember, this article provides general information and is not a substitute for professional medical advice. Always consult with your healthcare provider regarding your lab results and health decisions.