Red Blood Cell (RBC) Indices

Why this test may be ordered

• As part of a routine checkup
• If you have symptoms of anemia such as shortness of breath, weakness, fatigue, headache, dizziness, arrhythmia, pale skin, or cold hands and feet

Preparation and collection

You don't need any special preparations for a red blood cell (RBC) indices test.

A health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This test usually takes less than five minutes.

There is very little risk to having a blood test. There may be slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.

Understanding results

You will get results for each of the indices. Abnormal results may include one or more of the following.

• Smaller than normal red blood cells (low MCV): If your red blood cells are smaller than normal, it may mean you have: Iron deficiency anemia, the most common form of anemia. Thalassemia, which is a group of blood disorders that are inherited (passed down through families). Limitation: Your provider will consider your symptoms, medical history, and the results of other blood tests to understand your results. Next step: Talk to your health care provider if you have questions about your results.
• Larger than normal red blood cells (high MCV): If your red blood cells are larger than normal, it may mean you have: Anemia caused by a vitamin B deficiency, Liver disease. Limitation: Your provider will consider your symptoms, medical history, and the results of other blood tests to understand your results. Next step: Talk to your health care provider if you have questions about your results.
• Higher than normal MCHC: If the average amount of hemoglobin is higher than normal, it may mean you have: Hemolytic anemia, a type of anemia that happens when red blood cells are destroyed faster than they can be replaced. Hereditary spherocytosis, a rare genetic disorder that causes anemia and gallstones. Limitation: Your provider will consider your symptoms, medical history, and the results of other blood tests to understand your results. Next step: Talk to your health care provider if you have questions about your results.
• Red cell distribution width (RDW) not normal: If your results were not normal, it means there are differences in the size of your red blood cells. Limitation: This measurement is not enough for your provider to make a diagnosis, so RDW results are usually combined with the results of other indices and other blood tests. Next step: This combination of results can help confirm a diagnosis.

• Reference ranges and units are not provided in the source; interpretation should be done by your healthcare professional.
• RDW results alone are not diagnostic and must be combined with other indices and tests.

What to do next

Talk to your health care provider if you have questions about your results. Your provider will consider your symptoms, medical history, and the results of other blood tests to understand your results.

• What do my RBC index results mean for my health?
• Do I need any additional tests?
• What type of anemia might I have based on these results?
• What are the next steps for treatment or monitoring?

Evidence source

Source: U.S. National Library of Medicine (MedlinePlus). Practices and reference ranges may differ in your country.

U.S. National Library of Medicine: Red Blood Cell (RBC) Indices

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