high red blood cell distribution width

4 min read 08-03-2025

Meta Description: Discover what a high red blood cell distribution width (RDW) means. This comprehensive guide explores the causes, symptoms, diagnosis, and treatment of elevated RDW, a key indicator of various health conditions. Learn how RDW testing helps assess your overall health and what steps you can take if your results show an elevated RDW. We'll examine different conditions associated with high RDW, from anemia to other underlying health issues, providing a clear understanding of this important blood test.

Introduction:

A high red blood cell distribution width (RDW) indicates variation in the size of your red blood cells. Your doctor may order an RDW test as part of a complete blood count (CBC). While a slightly elevated RDW isn't always cause for alarm, a significantly high reading can signal underlying health problems. This article provides a detailed overview of high RDW, its causes, and what you need to know.

What is Red Blood Cell Distribution Width (RDW)?

RDW is a measurement of the variation in the size of your red blood cells (erythrocytes). Red blood cells are responsible for carrying oxygen throughout your body. They are typically uniform in size. However, various conditions can lead to an increase in the size variation, resulting in a high RDW. This is often detected during a routine complete blood count (CBC) test.

Understanding the RDW Measurement

RDW is expressed as a percentage. A normal RDW typically ranges from 11.5% to 14.5%, although this can vary slightly depending on the laboratory. An RDW above the normal range suggests anisocytosis—meaning there's a higher than normal variation in the size of your red blood cells.

What Causes a High RDW?

Several factors can contribute to an elevated RDW. The most common causes include:

1. Anemia

Many types of anemia are associated with high RDW. These include:

Iron-deficiency anemia: This is the most common type of anemia, often caused by insufficient iron intake or blood loss. The body cannot produce enough healthy red blood cells, leading to variations in size.
Vitamin B12 deficiency anemia: A deficiency in vitamin B12, often due to poor diet or malabsorption, can also result in abnormally sized red blood cells.
Folate deficiency anemia: Similar to B12 deficiency, a lack of folate, crucial for red blood cell production, leads to variations in cell size.
Thalassemia: This inherited blood disorder affects hemoglobin production, impacting red blood cell size and shape.
Aplastic anemia: This rare condition involves the bone marrow's failure to produce sufficient blood cells, resulting in varied red blood cell sizes.
Sickle cell anemia: This inherited disorder causes abnormal hemoglobin, resulting in misshapen and varied-sized red blood cells.

2. Other Medical Conditions

Besides anemia, other health problems can cause a high RDW. These include:

Chronic kidney disease: Kidney disease can affect the production of erythropoietin, a hormone necessary for red blood cell production.
Hypothyroidism: An underactive thyroid gland can slow down red blood cell production.
Alcohol abuse: Chronic alcohol consumption can damage the bone marrow and impair red blood cell production.
Certain cancers: Some cancers can interfere with red blood cell production.
Myelodysplastic syndromes (MDS): These are a group of bone marrow disorders that can affect red blood cell production.

3. Medications

Some medications can also contribute to a high RDW, though it's usually a less common factor.

Symptoms of High RDW

A high RDW itself doesn't typically cause noticeable symptoms. Instead, the symptoms you experience are often related to the underlying condition causing the elevated RDW. Common symptoms associated with conditions that often lead to high RDW include:

Fatigue: Feeling unusually tired or weak.
Shortness of breath: Difficulty breathing, even during light activities.
Palpitations: A racing or irregular heartbeat.
Pale skin: A noticeably paler complexion than usual.
Headaches: Frequent or severe headaches.
Dizziness: Feeling lightheaded or faint.

Diagnosing a High RDW

Your doctor will likely order a complete blood count (CBC) as part of a routine checkup or if you're experiencing symptoms mentioned above. The CBC includes an RDW measurement. If your RDW is elevated, further tests might be necessary to determine the underlying cause, such as:

Peripheral blood smear: A microscopic examination of your blood to examine red blood cell morphology (shape and size).
Iron studies: To assess iron levels in your body.
Vitamin B12 and folate levels: To check for deficiencies.
Bone marrow biopsy: In some cases, a sample of bone marrow is examined to evaluate blood cell production.

Treating a High RDW

Treatment for a high RDW focuses on addressing the underlying cause. This might involve:

Iron supplements: For iron-deficiency anemia.
Vitamin B12 or folate supplements: For deficiencies in these vitamins.
Medication: For conditions like hypothyroidism or chronic kidney disease.
Lifestyle changes: Such as dietary adjustments and abstaining from alcohol.
Blood transfusions: In severe cases of anemia.
Chemotherapy or other cancer treatments: If cancer is the underlying cause.

When to See a Doctor

If you experience symptoms like fatigue, shortness of breath, or pale skin, it's important to consult your doctor. They can perform the necessary tests, including an RDW measurement, to determine the cause and recommend appropriate treatment.

Conclusion

A high RDW is not a disease in itself but rather an indicator of a possible underlying health problem. While a slightly elevated RDW may not be cause for immediate concern, a significantly high reading requires further investigation to identify and treat the root cause. Early diagnosis and treatment are crucial for managing conditions associated with a high RDW and improving your overall health. Remember to consult your doctor for any concerns regarding your blood test results. They can provide personalized advice based on your individual health status.