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Red Cell Distribution Width (RDW)

The red cell distribution width blood test determines the amount of red blood cell variation in volume and size.

Anything outside of the normal range in red blood cell width or volume shows a possible problem with bodily function that may affect oxygen getting to various parts of your body.

Red cell distribution width is elevated if the range of sizes is large. Normal red blood cells are having a standard size of 6 to 8 micrometers (µm) in diameter.

RDW is not used as an only parameter when determining a complete blood count (CBC). Rather, it helps to provide shades of meaning in the context of the hemoglobin and mean corpuscular value.

High Red cell distribution width values may mean your body has a nutrient deficiency, anemia, or other underlying condition.

Why is the RDW test done?

The RDW test is done to diagnose types of anemia and other medical conditions such as

  • thalassemias,
  • Cancer
  • Liver disease
  • Diabetes mellitus
  • Heart disease

This test is mainly performed as a part of a complete blood count (CBC).

Doctors may also consider at the RDW test as part of a CBC if you have:

  • anemia symptoms
  • an iron or vitamin deficiency
  • a family history of a blood disorder
  • Significant blood loss from surgery or trauma
  • Disease that affects red blood cells
  • Chronic illness, such as  AIDS or HIV

What preparation do we need for the test?

RDW Blood test usually done as part of a complete blood count (CBC).So no preparations are needed before the test. The test can be easily conducted in any lab or blood testing centre. You generally don’t need any special preparations for an RDW blood test. Your doctor will let you know if there are any special instructions to follow.

Normal range for an RDW test

  • Normal red cell distribution width is 12.2 to 16.1 percent in adult females
  • Normal red cell distribution width 11.8 to 14.5 percent in adult males

You may have nutrient deficiency, infection, or other disorder if you score outside this range,These ranges may change depending on the laboratory or doctor

High results

If your Red cell distribution width is too high, it may be an indication of a nutrient deficiency, such iron, folate, or vitamin B-12. It also indicates that you have macrocytic anemia.

To diagnose the condition properly your doctor orders CBC test and compare the RDW and MCV test portions to measure your red blood cell volume.

A low MCV with a high red cell distribution width occurs in microcytic anemias.A high MCV with a high red cell distribution width occurs in some macrocytic anemias.

Normal results

If you receive a normal Red cell distribution width with a low MCV, you may have an anemia from a chronic disease

Low results

There are no hematologic disorders linked with a low Red cell distribution width result.

Authenticated by:

Dr. Gaurav Sharma

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