Red Cell Distribution Width (RDW) Blood Test: What Is It For?

Disease that connected to red blood cells is nearly common today it can be because of human lifestyle, genetics and environmental influence. That’s why medical practitioners and experts formulate and develop different blood tests to determine human’s disease that link to blood.

A hand with white gloves holding a blood sample

Many people are now being advised to go for regular checkups. So with regular checkups, your doctor would recommend that you do some tests. One of the common tests done is a blood test. Usually, a complete blood count is done. And when a complete blood count is done it indicates different things. With a complete blood count, you can tell if the patient is anemic or has an infection. One example of blood test is the RDW blood test. It measures the amount of RBC variation in terms of volume and size.

The results of this test sure indicate a lot. Over the years the result of the RDW blood test has helped doctors to confirm if a person has anemia. Anemia is when there’s a lack of RBCs in the blood. At the same time, this RDW blood test can help in determining the cause of anemia. A study that was conducted showed that this blood test helps predict mortality in people over 45 years of age. So we’ll take a closer look at what this test is all about. Also, we’ll have a look at how to prepare for it.

What is RDW Blood Test? 

This is a blood test that shows the difference in size between red blood cells. It would usually compare the smallest of RBCs to the largest RBCs. An average RBC is about 6-8 micrometers in diameter. But variation is a bit common among red blood cells.

As you may already know, red blood cells transport oxygen in the body. they transport it from the lungs to every other part of the body. There’s a protein component inside RBCs. It’s known as hemoglobin. Hemoglobin binds to oxygen and then transports it.

Normally, the shape, size, and health of RBCs would affect the transfer of oxygen. Another thing that affects the transport of oxygen is a problem with hemoglobin. And this can actually cause a variety of health problems.

This test is carried out to either evaluate anemia or other conditions such as:

This test is actually part of CBC. Your doctor would actually help order for CBC due to these different reasons:

  • When you have anemia symptoms like numbness, pale skin and dizziness
  • When you’re iron deficient or vitamin deficient 
  • Family history of blood disorders 
  • When a significant amount of blood is lost from trauma or surgery 
  • When you have a disease that has to do with red blood cells 
  • Chronic illnesses such as HIV

How to Prepare for the Test

This test isn’t much of a big deal. It’s a test that you would be done within just 5 mins. Sometimes, they might need you to fast just before doing the test. If your doctor has ordered other tests then that’s when fasting might be necessary. As for any other special instruction, your doctor would give you before you carry out the blood test.

What the healthcare provider does is just get blood from your vein. And then the blood drawn is stored in a tube. That’s about it. Once the needle is removed the healthcare provider would put a small bandage on the needle site. And request you to apply a bit of pressure. This is to stop the bleeding at the needle site. Then the tube would be sent to the lab. Just in case the needle site is still bleeding after long hours visit a doctor. This is not so common though. 

Well, with this test there’s very little risk involved. You could experience a bit of pain and bruise at the needle site but that’s just about it. After a while, the pain and bruise would disappear. So you have nothing to worry about. 

Interpretation of Results

The normal range for an adult female is about 11.9-15.5%. For an adult male, it’s about 11.8-15.6%. The thing though is that a normal result doesn’t mean there’s no underlying condition. That’s why doctors use other blood tests to consider the state of health of the person. Usually, your doctor would compare your RDW result with your MCV result. MCV checks for the average volume of an RBC.

  • When RDW and MCV are normal: There could still be anemia. And it could be as a  result of a chronic condition or even blood loss.
  • When RDW is normal and MCV is low: It could be anemia caused by either thalassemia or a chronic medical condition.
  • When RDW is normal and MCV is high: This could be a liver problem or too much consumption of alcohol.

High results of RDW is indicative of a nutrient deficiency. It could either be a deficiency in iron, vitamin B-12 or folate. Also, it could indicate macrocytic anemia. This is a condition wherein the body doesn’t produce enough normal RBCs. When it does produce RBCs it’s usually larger than the average RBC. This can be caused by a deficiency in either vitamin B-12 and folate.

It may also indicate microcytic anemia. This, on the other hand, is a condition wherein there’s a deficiency in normal RBC. In this condition, the RBCs are smaller than they should be. The deficiency of iron is known to be a common cause of microcytic anemia.

For better diagnosis, it’s compared with MCV. When the results show low MCV and high RDW that’s microcytic anemia. And when both MCV and RDW are high it indicates macrocytic anemia.

Low results of RDW have no medical implications. Low RDW result isn’t associated with hematologic disorders.

Anemia is treatable. So relax a bit. The first thing your doctor would have to do is reach a definite diagnosis. Then, your doctor would recommend some supplements and medications. Also, your doctor can recommend some changes to your diet. If after you start the supplements and medications, you notice any strange symptoms contact your doctor as soon as you can. As long as you follow all these you can expect good results when next you have an RDW blood test. 

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