RDW Blood Test: High and Low RDW Meaning
RDW measures variation in red blood cell size. Normal values are about 11.5–15%. High RDW indicates uneven cell sizes often linked to anemia, while low RDW usually has little clinical significance.
Contents
Result interpretation RDW
What your result means based on common reference ranges
Red blood cells are uniform in size, indicating stable production and no active deficiency.
Slight variation in cell size suggests early nutritional deficiency or a recovery phase.
Large variation indicates active anemia or mixed red blood cell populations requiring evaluation.
Cells are very uniform in size, which is typically not clinically significant.
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What is RDW?
RDW (Red Cell Distribution Width) is part of a complete blood count and reflects how uniform your red blood cells are in size. Healthy cells are similar in size, allowing efficient oxygen transport. When RDW increases, it indicates a mix of small and large cells, often due to nutrient deficiencies or bone marrow response to stress. It is frequently used alongside MCV to identify specific types of anemia and detect early changes in blood health.
Reference ranges
Causes of abnormal values
Causes of low RDW
- • Uniform macrocytosis — all cells consistently large
- • Uniform microcytosis — all cells consistently small
- • Genetic factors — naturally uniform red blood cell population
Causes of high RDW
- • Iron deficiency anemia — production of smaller cells alongside normal ones increases variation
- • Vitamin B12 deficiency — leads to large immature red blood cells
- • Folate deficiency — disrupts normal cell maturation causing size differences
- • Recent blood transfusion — mixing donor and patient cells increases variability
- • Hemolytic anemia — rapid destruction triggers release of immature larger cells
- • Liver disease — alters red blood cell membrane formation
- • Chronic inflammation — disrupts iron metabolism and cell production
RDW in combination with other markers
Possible symptoms
- •Persistent fatigue
- •Shortness of breath
- •Pale or yellowish skin
- •Dizziness or lightheadedness
- •Cold hands and feet
When to see a doctor
Consult a doctor if RDW is above 16% alongside symptoms such as fatigue or shortness of breath. Seek evaluation if results remain abnormal over time or are combined with low hemoglobin.
What to do if abnormal
- Consult a doctor for interpretation
- Check iron, B12, and folate levels
- Correct deficiencies through diet or supplements
- Repeat blood test after 2–3 months
- Maintain proper hydration
The information on this page is intended for general understanding of test results and does not replace medical consultation. Accurate interpretation requires considering other blood markers and individual factors.
Content is based on medical literature and used within the PulseBook analytical system.
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