RDW Blood Test: Key Roles, Normal Levels, and Health Impacts

What Is RDW?

RDW (Red Cell Distribution Width) is a measurement that shows the range of sizes of red blood cells (RBCs) in your blood sample.

Red blood cells are crucial for transporting oxygen from the lungs to the rest of the body, and their size can vary depending on a person's health status. RDW specifically looks at this size variability and helps doctors understand if there is an issue with how these cells are being produced or maintained in the body.

A healthy body tends to produce red blood cells that are relatively uniform in size, but certain health conditions can cause significant size variations.

By measuring RDW, healthcare professionals gain insights into whether your body is struggling with issues like nutrient deficiencies, chronic diseases, or blood disorders.

When Is RDW Testing Recommended?

Doctors may recommend this test for a variety of reasons. Here are common situations where RDW testing might be prescribed:

• Signs of anemia, such as dizziness, weakness, or pale skin
• Long-term infections that are difficult to treat
• Problems with the gastrointestinal tract, which could affect nutrient absorption
• A family history of inherited blood disorders
• Significant blood loss, either from an injury or surgery
• Concerns about a diet low in minerals or iron
• General health check-ups, especially if you're experiencing fatigue or low energy

How Is RDW Testing Conducted?

RDW is measured through a blood test, specifically as part of a Complete Blood Count (CBC). A small sample of blood is taken, usually from a vein in your arm, and sent to the laboratory for analysis.

The CBC not only measures RDW but also looks at other components of your blood, including red and white blood cell counts and platelets.

The RDW test calculates how much the size of your red blood cells varies by first measuring the Mean Corpuscular Volume (MCV), which represents the average size of your red blood cells. After MCV is determined, a special formula is used to calculate RDW.

Special Preparations for RDW Testing

To ensure accurate results, here are a few things to keep in mind before getting your RDW tested:

• Do not eat for at least 8 hours before the test; only water is allowed.
• Avoid drinking alcohol for at least 24 hours before the test.
• Refrain from smoking and avoid any physical or emotional stress 30 minutes before the test.
• It's a good idea to wear comfortable clothing and stay hydrated before your appointment to make the blood draw easier.

What Are the Normal RDW Levels?

The normal range for RDW in adults is typically between 11.5% and 14.5%.

Note: The units of measurement and the normal ranges can differ depending on the laboratory and the specific methods used.

What Do Abnormal RDW Levels Mean?

RDW High Levels

A high RDW indicates that there is a significant variation in the size of your red blood cells. This can be a sign of various health issues. Some of the most common causes of elevated RDW levels include:

• Different types of anemia: Deficiencies in vitamins B9 and B12, or iron, can lead to anemia, causing your red blood cells to vary in size.
• Pregnancy: During and after pregnancy, RDW levels can temporarily rise as the body adjusts to changes in blood production.
• Dietary deficiencies: A lack of minerals, especially iron, can affect red blood cell production, causing size variations.
• Chronic diseases: Conditions like diabetes, Crohn’s disease, and other long-term illnesses can impact red blood cell health.
• Blood loss: After significant blood loss (e.g., due to surgery or injury), your body may struggle to replace red blood cells, leading to increased size variation.
• Chemotherapy: Certain types of chemotherapy can affect red blood cell production and result in higher RDW.
• Inherited blood disorders: Some hereditary conditions, such as thalassemia, can cause RDW to rise.

• Improve diet: Focus on consuming foods rich in iron (like spinach, red meat, and legumes) and vitamins B9 and B12 (such as leafy greens, fortified cereals, and dairy products).
• Regular check-ups: If you have a chronic illness, follow up with your doctor regularly to monitor your RDW levels.
• Hydrate and rest: Proper hydration and sufficient rest help maintain healthy blood production.
• Consult a specialist: If RDW levels remain high, see a healthcare professional for further investigation.

RDW Low Levels

While low RDW levels are rare, they generally aren’t considered a cause for concern. However, in some cases, they may suggest issues like:

• Uniform red blood cell size: Low RDW can simply mean that your red blood cells are all relatively the same size, which may indicate certain types of anemia.
• Bone marrow disorders: In rare cases, low RDW may signal problems with how your bone marrow is producing red blood cells.

• Monitor overall health: Continue regular health check-ups to ensure there are no underlying issues causing low RDW.
• Balanced nutrition: Eat a nutrient-rich diet to support red blood cell health.
• Consult a healthcare professional: If low RDW is associated with other abnormal blood markers, further testing may be required.

Which Specialist Should You Consult?

If your RDW levels are abnormal, the type of specialist you should consult depends on the underlying issue suspected. Here are some of the professionals you might be referred to:

• Hematologist: A doctor specializing in blood disorders, ideal for diagnosing anemia and other red blood cell issues.
• Gastroenterologist: If RDW levels suggest problems with nutrient absorption, you may need to see a gastroenterologist.
• Endocrinologist: If chronic conditions like diabetes are affecting your RDW, an endocrinologist can help.
• Primary care physician: For less severe concerns or as a first step, your family doctor or primary care physician can guide you in managing abnormal RDW levels.