Red cell distribution width (RDW) test and its importance

Contribution: Rachna Arya


Size matters when it comes to your red blood cells. Healthy red blood cells are roughly the same size.

Red blood cells that are completely different sizes from each other (high variation) can be a sign of anemia, a blood disorder in which there are not enough healthy red blood cells to deliver enough oxygen to all parts of the body.

This blog explores the RDW test and explains the results in a range of different ways.

What is red cell distribution with (RDW) test?

An RDW blood test is a standard component of a routine Complete blood count test. The RDW value tells you if there is a change in red blood cell size or red blood cell volume.

It is used in conjunction with other red blood cell indices, particularly mean corpuscular volume (MCV), to help determine the cause of anemia.

What does the RDW blood test measure?

The term ‘width’ in red cell distribution width may seem like a confusing term.

For those not in the medical profession, it’s easy to assume that the test is related to the width of your red blood cells.

However, this is not the case. Instead, an RDW blood test measures the difference in size and shape between the smallest and largest red blood cells in a representative sample.

Cell distribution width refers to the distance between red blood cell sizes.

Cells of similar size are clustered together and the RDW result will be lower.

Cells of different sizes will show a wider distribution of values ​​and the RDW will be higher

When will the RDW blood test be necessary?

An RDW can be a useful number to help your doctor diagnose if you have any blood-related disorders and diseases.

Anemia symptoms

Your healthcare provider may order an RDW blood test to get an idea of ​​whether anemia is causing your symptoms, which usually include:

  • tiredness
  • shortness of breath
  • feeling cold
  • head spinning
  • Pale or dry skin
  • headache

Conditions associated with anemia

An RDW blood test, along with other RBC indicators, can be used to indicate the specific type of anemia you have and what is causing the anemia. Conditions linked to anemia include:

What do RDW blood test results mean?

RDW test results tell your healthcare provider if your RDW levels are within normal limits or if they are changing in size and volume.

Normal RDW

A normal result maintains an ideal size of 6 to 8 micrometers in diameter and means that your red blood cells are uniform in size and shape.

High RDW

An elevated level of RDW indicates that your red blood cell size varies outside the normal threshold. This could be a sign of anemia or a related condition.


A low RDW is usually not a cause for concern and is normal and desirable.

Last thought

In recent years, many clinical studies have proven that the RDW parameter is a strong predictor of your health.

It provides a key prognostic marker to determine various points about your health, from iron deficiency to acute and chronic heart failure (HF).

However, it is important to remember that no matter what the RDW numbers indicate, further evaluation and tests are always necessary to help determine potential health disorders and how they should be treated.

Therefore, it is important to keep your blood iron levels in the optimal range to avoid anemia and related complications. The best way to achieve this is by taking all natural Ayurvedic supplements that have almost no side effects.

Buy your all natural iron supplement today!

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