What You Need To Know About RDW Blood Test

An RDW blood test is part of a complete blood count (CBC). It looks at how much your red blood cells differ in size. A big mix of sizes equals higher RDW. While mostly the same size means lower RDW. By itself, RDW doesn’t provide a diagnosis, but it helps explain symptoms such as tiredness, pale skin, shortness of breath, and other signs of anemia when read in conjunction with the rest of your CBC. You can easily run the test at MyCyberClinic and have a doctor attend to you.

What is RDW in Blood Test?

Has the doctor sent you for an RDW test, and you are wondering, “What is RDW in Blood Test?” RDW means Red Cell Distribution Width. It is a number on your complete blood count that shows how much your red blood cells differ in size.

What is RDW?

Think of red blood cells like beads. These blood cells come in different sizes. The RDW test is simply a test that shows a score of how mixed those sizes are.

Why and when doctors order an RDW blood test

Doctors order an RDW blood test with most CBCs. During checkups, before surgery, or when you’re tired, weak, dizzy, short of breath, or look pale. It helps decide which follow-up tests to run and whether a treatment is working.

RDW Blood Test High

Seeing RDW blood test high means your red cells vary a lot in size. That often happens when your body is making new cells to catch up, or when it’s missing key nutrients.

Common causes of RDW blood test high

• Low iron
• Low vitamin B12 or folate
• A mix of problems (for example, low iron and low B12)
• Recent blood loss or breaking down red cells faster (hemolysis)
• Liver disease or heavy alcohol use
• Bone-marrow problems

What to do next

If RDW blood test high appears on your report:

• Check the rest of the CBC (especially MCV and hemoglobin).
• Do focused labs: iron studies (including ferritin), vitamin B12, folate.
• Talk about diet, medicines, alcohol, heavy periods, or gut bleeding.
• Treat the cause, then repeat the RDW blood test to see if it’s improving.

RDW Blood Test Low

A RDW blood test low result is less common and usually not a problem by itself. It often just means your red cells are very similar in size.

When Does A Low RDW Appear

A low RDW appears when there is:

• Normal health with uniform red cells
• Small lab-to-lab differences in how RDW is measured
• Certain inherited patterns where cells are all small but similar.

Practical next steps

If you feel fine and everything else looks normal, RDW blood test low usually needs no action. If you have symptoms or other abnormal results, your doctor may repeat the CBC and add tests like iron studies or hemoglobin checks to look for a cause.

Conclusion

RDW is a helper number. Knowing what is RDW in blood test makes your CBC easier to read. RDW blood test high can point to low iron or vitamins while RDW blood test low is usually nothing serious. The goal is simple. Find the cause, treat it, and recheck. If results don’t match how you feel, speak up. Data and symptoms should make sense together.

FAQs

1. What does the RDW blood test actually measure?

RDW blood test measures how different in size your red blood cells are. 

2. Is a RDW blood test high always serious?

Not always. RDW blood test high is common with low iron or vitamins and often improves after treatment.

3. What should I do after a RDW blood test high result?

Review MCV, hemoglobin, iron/ferritin, vitamin B12, and folate with your doctor. Treat the cause and recheck the RDW blood test.

4. What if my report shows RDW blood test low?

RDW blood test low is usually nothing to worry about. Confirm with a repeat test if needed and look at the rest of the CBC.