High RDW Blood Test Results – Everything You Need to Know

RDW testing
What does RDW mean in a blood test?

Today we’re going to talk about what does RDW mean in a blood test.

What does RDW mean in Blood Work?

The Red blood cell Distribution Width (RDW) is a measurement of your Red Blood Cell (RBC) volume.

Your RDW levels are always provided when you get a standard complete blood count test (CBC).

Typical red blood cells that are healthy have a standard size of about 6-8 μm in diameter.

If your sizes are different than this, it can be a sign that there is a potential disorder.

What Does it Mean when Your RDW Test Results are High?

When your red cells have a lot of variation in their size then you will see higher RDW values in your test.

If your RDW blood test is high then there could be a few reasons for the cause.

A common cause of high RDW values is Vitamin b12 deficiency or Folate deficiency.

This can lead to macrocytic anemia or large cell anemia. (People with macrocytic anemia almost always suffer from elevated RDW levels.)

When an elevated RDW level is observed the common practice is to test RDW results against a mean corpuscular volume test (MCV).

With these deficiencies, a person will usually see high RDW and high MCV results.

With the combined results your doctor can learn more about the condition. This tells them if one or many factors are to blame.

Iron deficiency anemia can also increase your RDW levels.

When both iron and b12 are deficient it’s common to see both large and small red blood cells. This makes your RDW levels show high levels of elevation. Iron deficiency usually shows high RDW and low MCV results.

When this happens it’s called anisocytosis.

Now, elevated RDW doesn’t always show up with anemia. There are different forms of anemia which don’t always have that result.

Note that you can still have normal RDW levels if you have anemia from chronic disease, acute blood loss, aplastic anemia, spherocytosis or hemoglobinopathies.

How to Treat (Lower) your High RDW Levels

You can support healthy RDW levels through diet and supplementation.

Doctors often recommend getting more B-12.

B-12 is abundant in animal products. You can also supplement it. I recommend the methylated form of B-12 here.

Folate is also important to bring down RDW levels (and increase Ferratin).

You can get folate in green vegetables, peanuts, beef liver, chicken, cod, oysters, tuna etc.

You can also supplement it. I recommend this methylated folate supplement.

What about Normal RDW levels?

Hopefully your just fine then if your levels are normal!

But if your here, maybe you think it’s something else. Especially if anemia is present.

If you have both anemia and normal RDW levels then it could be thalassemia. In this case, the Mentzer Index should from the CBC report to be investigated to confirm.

RDW is useful in the following conditions:

  • Elevated RDW helps provide a clue for a diagnosis of early nutritional deficiency such as iron, folate, or vitamin B12 deficiency as it becomes elevated earlier than other red blood cell parameters.
  • It aids in distinguishing between uncomplicated iron deficiency anemia (elevated RDW, normal to low MCV) and uncomplicated heterozygous thalassemia (normal RDW, low MCV); however, definitive tests are required.
  • It can also help distinguish between megaloblastic anemia such as folate or vitamin B12 deficiency anemia (elevated RDW) and other causes of macrocytosis (often normal RDW).
  • RDW can be used as a guidance for flagging samples that may need manual peripheral blood smear examination, since elevated RDW may indicate red cell fragmentation, agglutination, or dimorphic red blood cell populations.

RDW along with mean corpuscular volume (MCV) is helpful in narrowing the cause of anemia:[6]

Normal RDW and low MCV are associated with the following conditions:

  • Anemia of chronic disease
  • Heterozygous thalassemia
  • Hemoglobin E trait

Elevated RDW and low MCV are associated with the following conditions:

  • Iron deficiency
  • Sickle cell-β-thalassemia

Normal RDW and high MCV are associated with the following conditions:

  • Aplastic anemia
  • Chronic liver disease
  • Chemotherapy/antivirals/alcohol

Elevated RDW and high MCV are associated with the following conditions:

  • Folate or vitamin B12 deficiency
  • Immune hemolytic anemia
  • Cytotoxic chemotherapy
  • Chronic liver disease

Normal RDW and normal MCV are associated with the following conditions:

Elevated RDW and normal MCV are associated with the following conditions:

  • Early iron, vitamin B12, or folate deficiency
  • Dimorphic anemia (for example, iron and folate deficiency)
  • Sickle cell disease
  • Chronic liver disease
  • Myelodysplastic syndrome

1 thought on “High RDW Blood Test Results – Everything You Need to Know”

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