In this article

What is RDW?

RDW, or red cell distribution width, is a blood test parameter that measures the variation in the size of your red blood cells. It is reported as a percentage and calculated from the standard deviation of red blood cell volume divided by the mean corpuscular volume (MCV). RDW is typically included as part of a complete blood count (CBC) panel. A higher RDW value indicates greater variation in red blood cell size, a condition known as anisocytosis, while a lower RDW value indicates more uniform red blood cell size.

Why is RDW Important?

Tracking your RDW levels provides valuable insight into your overall health and can help identify various medical conditions. RDW is particularly useful in diagnosing and differentiating types of anemia, as different forms of anemia produce different patterns of red blood cell size variation.

High RDW may indicate several conditions including iron deficiency anemia, vitamin B12 or folate deficiency, hemolytic anemia, or mixed types of anemia. It can also be elevated in chronic diseases, liver disease, or cardiovascular conditions. Research has shown that elevated RDW is associated with increased inflammation and oxidative stress in the body.

Low RDW is less common and typically indicates that red blood cells are relatively uniform in size, which is generally normal, though it can occasionally be seen in certain chronic anemias or blood disorders. If you are concerned with your levels, it is important to consult with your physician for proper interpretation in the context of your overall health profile.

How Can I Better Understand My RDW Levels?

RDW results are most useful when analyzed together with other red blood cell parameters such as MCV, hemoglobin, and hematocrit to determine the underlying cause of any abnormalities. When RDW is elevated alongside low MCV, it may suggest iron deficiency anemia. When RDW is elevated with high MCV, it may point to vitamin B12 or folate deficiency. Normal RDW with low MCV might indicate thalassemia trait, while normal RDW with normal MCV is typically seen in healthy individuals or certain chronic diseases.

RDW-CV (Coefficient of Variation):

  • Normal: 11.5 – 14.5%
  • Borderline: 14.6 – 15.0%
  • High: >15.0%

RDW-SD (Standard Deviation):

  • Normal: 39 – 46 fL
  • High: >46 fL

How Can I Maintain Optimal RDW Levels?

Dietary Changes

Ensure adequate intake of iron through foods like lean meats, beans, and fortified cereals. Include foods rich in vitamin B12 such as fish, meat, and dairy products, and folate from leafy greens and legumes. Vitamin C enhances iron absorption, so pairing iron-rich foods with citrus fruits or bell peppers is a simple and effective strategy.

Lifestyle Changes

Managing chronic inflammation through regular exercise, adequate sleep, and stress reduction supports healthy red blood cell production. Avoid excessive alcohol consumption, which can interfere with nutrient absorption and red blood cell development. If you have been diagnosed with a nutritional deficiency, follow your healthcare provider’s recommendations for supplementation.

Where Can I Learn More?

DISCLAIMER: IF YOU ARE CONCERNED WITH ANY OF YOUR RESULTS, PLEASE CONSULT WITH YOUR PHYSICIAN.