Blood Count
Red Blood Cell Distribution Width (RDW)
Blood Count
Measures variation in red blood cell size. Elevated in iron deficiency, B12/folate deficiency and chronic disease.
VAT-exempt medical service
Erc(B)-RDW (Red Cell Distribution Width) analyzes the variation in size among your red blood cells. Healthy individuals have relatively uniform cell sizes. When cells vary greatly (anisocytosis), it often points to nutritional deficiencies, bone marrow disorders, or mixed anemias. RDW is typically interpreted alongside MCV, hemoglobin, and hematocrit.
RDW is particularly useful for distinguishing between types of anemia. For example, iron-deficiency anemia often shows high RDW with low MCV, while thalassemia shows normal RDW with low MCV. The test also helps evaluate nutritional status and monitor recovery from anemia treatment.
What a high value can mean
A high RDW indicates large variation in red blood cell size (anisocytosis). This may occur with iron deficiency, combined iron and B12/folate deficiency, recovery from blood loss, hemolytic anemia, or bone marrow disorders.
What a low value can mean
A normal or low RDW suggests uniform red blood cell size and is typical in healthy individuals. Some anemias, such as thalassemia minor, also present with normal RDW.
No special preparation is required. Bring valid ID to your appointment.
Order your test
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Give your sample
Visit any of our partner sampling locations. No appointment needed at most of them.
The lab analyses it
Your sample is analysed at an accredited Swedish laboratory.
Get your results
Your values appear in your account with reference ranges and an explanation of each marker.
This combination often indicates iron-deficiency anemia, where red blood cells are both smaller and more variable in size than normal.
Yes. RDW can be elevated during recovery from blood loss or nutrient supplementation, even before other markers normalize.
Yes. RDW is a standard component of a complete blood count (CBC) and is automatically calculated by most hematology analyzers.