Blood test

Normal RDW level in the blood

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Normal RDW level in the blood

What is the normal range of RDW?

Men: 11.5 - 14.5 %
Women: 11.5 - 14.5 %
Children: 11.5 - 14.5 %

Why normal levels can differ across different labs?

Each laboratory must establish its own normal ranges for RDW in the blood. These ranges depend on the makeup of the local population, the technologies used and the accuracy of the measurement. There may be also slight differences in the normal levels according to age, gender, race or ethnic origin, geographic region, diet, type of sample and other relevant status.

Your doctor will study the results along with your medical record, screenings, physical condition, symptoms and any other relevant information about your situation.

What is RDW?

RDW is the acronym of Red cell blood Distribution Width. The RDW as a numerical expression correlates with the degree of anisocytosis (unequal-sized cells).

Red Blood cells, also called erythrocytes, have a variable size. Its size is measured in femtoliters (10-15 liters). Normal RBCs have only a slight degree of variation. If RDW is high means that the RBCs are very different in size from each other.

What is RDW test used for?

RDW test is useful in case of hemoglobin is below the normal range (anemia). Clinicians may use the RDW to help differentiate various types of anemia along with the MCV (Mean Corpuscular Volume). This test is not helpful for persons who do not have anemia.

In case of anemia, RDW should be studied along with MCV to discern the different types of anemia in the following way:

  • If MCV is low (microcytosis) and RDW is high may be a sign of iron-deficiency anemia.
  • If MCV is high (macrocytosis) and RDW is high may be a sign of megaloblastic anemia.
  • If MCV is in the normal range and RDW is very high may be a sign of sideroblastic anemia.

In many other types of anemia, the RDW remains in the normal range such as in:

  • Anemia of chronic disease.
  • Posthemorrhagic anemia.
  • Aplastic anemia.
  • Thalassemia minor.
  • Anemia in chronic kidney disease.

The RDW can be helpful in distinguishing beta thalassemia minor (low MCV, normal RDW) from iron-deficiency anemia (low MCV, high RDW).

The RDW can be helpful in distinguishing anemia of chronic disease (low-normal MCV, normal RDW) from early iron-deficiency anemia (low-normal MCV, elevated RDW).

If MCV is high, it let discern between megaloblastic macrocytic anemias (due to vitamin B12 or folic acid deficiency) with high RDW from non-megaloblastic macrocytic anemias (alcoholism, antivirals, etc.) in which RDW is in the normal range.

A RDW percentage below the normal range has no clinical meaning. It is called isocytosis and it means that RBCs are very similar in size.

Where can I find more information about RDW level in the blood?

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Which values are considered a normal RDW level in the blood?

The following values are considered to be normal values:

IMPORTANT: These levels are expressed in %. They are an example of a healthy woman of about 45 years old with no known disease and not taking any medication. The ranges can be different depending on the laboratory or on your personal circumstances.

RDW
Normality
11.5 %11.6 %11.7 %11.8 %11.9 %12 %12.1 %12.2 %
12.3 %12.4 %12.5 %12.6 %12.7 %12.8 %12.9 %13 %
13.1 %13.2 %13.3 %13.4 %13.5 %13.6 %13.7 %13.8 %
13.9 %14 %14.1 %14.2 %14.3 %14.4 %14.5 % 
Last update: 12/01/2021

Bibliography

  • A Manual of Laboratory and Diagnostic Test. 9th edition. Frances Fischbach. Marshall B. Dunning III. 2014. Pag 100. ISBN-10: 1451190891.
  • Laboratory tests and diagnostic procedures with nursing diagnoses (8th ed), Jane Vincent Corbett, Angela Denise Banks, ISBN: 978-0-13-237332-6, Pag. 35.

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