What Level of Rdw Is Dangerous?

What Level of Rdw Is Dangerous

Red Cell Distribution Width (RDW) is a measure used in a Complete Blood Count (CBC) test to assess the variation in size and volume of red blood cells in the bloodstream. It’s an important marker that can provide insights into various health conditions. Understanding what RDW levels mean and when they might signal danger is crucial for maintaining good health.

So, let’s delve into the world of RDW and explore what levels could potentially be dangerous.

What is RDW?

Before we discuss dangerous levels, it’s important to grasp the basics. RDW measures the range in size and volume of red blood cells (RBCs) in a blood sample. Red blood cells are responsible for carrying oxygen from the lungs to the rest of the body. The width of the distribution of these cells can provide information about the uniformity of their size.

Typically, RDW results are given as a percentage. A normal range for RDW is between 11.5% and 14.5%. However, these values might slightly vary depending on the laboratory performing the test.

What Causes RDW to Increase?

Several factors can cause RDW levels to rise:


  • When there’s a deficiency in the number of red blood cells or hemoglobin, the body compensates by producing a wider range of red blood cell sizes, leading to an increased RDW.

Vitamin Deficiencies

  • Lack of certain vitamins, particularly vitamin B12 and folate, can lead to the production of abnormally sized red blood cells, contributing to higher RDW levels.

Chronic Diseases

  • Conditions such as liver disease, kidney disease, or autoimmune disorders can affect the production and lifespan of red blood cells, resulting in elevated RDW.

Bone Marrow Disorders

  • Any dysfunction in the bone marrow, where red blood cells are produced, can lead to the production of irregularly sized cells, causing an increase in RDW.

Interpreting RDW Levels

While a slightly elevated RDW might not necessarily indicate a serious health problem, persistently high levels could be a cause for concern. Here’s how to interpret different RDW levels:

Normal RDW (11.5% – 14.5%)

  • This indicates that the red blood cells are relatively uniform in size. In most cases, this range suggests good overall health.

Slightly Elevated RDW (14.5% – 15.5%)

  • A mild increase in RDW may not be alarming and could be due to various factors such as recent illness or minor nutritional deficiencies. However, it’s important to monitor and investigate further if it persists.

Moderately Elevated RDW (15.5% – 20%)

  • This range might indicate the presence of anemia or underlying health conditions. Further medical evaluation is necessary to determine the cause.

Severely Elevated RDW (> 20%)

  • RDW levels above 20% are considered significantly high and could signal serious health issues such as severe anemia, vitamin deficiencies, or chronic diseases. Immediate medical attention is required to diagnose and address the underlying problem.

What Level of Rdw Is Dangerous?

While there isn’t a specific threshold that defines when RDW levels become dangerous, persistent elevation beyond the normal range warrants attention. Factors such as the rate of increase, accompanying symptoms, and individual health history play a crucial role in determining the severity of the situation.

RDW becomes particularly dangerous when it indicates the presence of life-threatening conditions such as severe anemia, bone marrow disorders, or certain chronic diseases. In such cases, timely medical intervention is crucial to prevent complications and manage the underlying condition effectively.

Recognizing Symptoms

Understanding the symptoms associated with conditions that elevate RDW levels can help in early detection and treatment. Some common symptoms include:


  • Feeling unusually tired or weak, even after adequate rest, could be a sign of anemia or other underlying health issues.

Shortness of Breath

  • Difficulty breathing, especially during physical activity, might indicate reduced oxygen-carrying capacity of the blood due to anemia.

Pale Skin

  • A pale or jaundiced appearance could be indicative of underlying blood disorders or certain chronic diseases affecting red blood cell production.

Dizziness or Lightheadedness

  • Feeling dizzy or faint, particularly upon standing up, might suggest anemia or cardiovascular problems.

Irregular Heartbeat

  • An irregular or rapid heartbeat could be a sign of decreased oxygen supply to the heart due to anemia.

When to Seek Medical Help?

If you notice any persistent symptoms or if your RDW levels are consistently elevated during routine blood tests, it’s important to consult a healthcare professional promptly. Early diagnosis and treatment can significantly improve outcomes and prevent complications.

Medical professionals may recommend further tests such as additional blood work, imaging studies, or a bone marrow biopsy to determine the underlying cause of elevated RDW levels. Treatment will depend on the specific diagnosis but may include dietary changes, supplementation, medication, or other interventions tailored to address the underlying condition.


While RDW is just one of the many parameters evaluated in a Complete Blood Count, it can provide valuable insights into various aspects of health, particularly regarding red blood cell dynamics. Understanding what RDW levels mean and when they might indicate danger is essential for proactive healthcare management.

Regular health screenings, staying informed about personal health metrics, and seeking medical attention when necessary are crucial steps in maintaining overall health and well-being. Remember, early detection and intervention can make a significant difference in managing and treating underlying health conditions associated with abnormal RDW levels.

Written by Amy Fischer

Amy, a registered dietitian at the Good Housekeeping Institute's Nutrition Lab, brings a wealth of expertise to nutrition, health content, and product testing. With a journalism degree from Miami University of Ohio and a master's in clinical nutrition from NYU, she's a versatile expert. Prior to joining Good Housekeeping, Amy worked as a cardiac transplant dietitian at a prominent NYC hospital and contributed to clinical nutrition textbooks. Her background also includes PR and marketing work with food startups.

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