Results

A reticulocyte count is a blood test that measures how fast red blood cells called reticulocytes are made by the bone marrow and released into the blood.

Normal

The reticulocyte count is given as the percentage of red blood cells that are reticulocytes (the number of reticulocytes divided by the total number of red blood cells, multiplied by 100).

The normal values listed here-called a reference range-are just a guide. These ranges vary from lab to lab, and your lab may have a different range for what’s normal. Your lab report should contain the range your lab uses. Also, your doctor will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab.

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Newborns have a normal reticulocyte count of 2.5% to 6.5%. This value drops within 2 weeks to 0.5% to 2.0%.

High values

• A high reticulocyte count may mean more red blood cells are being made by the bone marrow. This can occur after a lot of bleeding, a move to a high altitude, or certain types of anemia. These conditions cause red blood cells to break down (hemolysis).
• The reticulocyte count rises after the treatment for pernicious anemia, iron deficiency anemia, or folic acid deficiency anemia starts working.

Low values

• A low reticulocyte count may mean fewer red blood cells are being made by the bone marrow. This can be caused by aplastic anemia or other types of anemia, such as iron deficiency anemia.
• A low reticulocyte count can also be caused by exposure to radiation, a long-term (chronic) infection, or by certain medicines that damage the bone marrow.

What Affects the Test

Reasons you may not be able to have the test or why the results may not be helpful include:

• Taking certain medicines. Medicines that affect the results include ones used for Parkinson's disease, rheumatoid arthritis, fevers, malaria, and cancer chemotherapy.
• Getting radiation therapy.
• Taking sulfonamide antibiotics (such as Septra).
• Being pregnant.
• Having a recent blood transfusion.

What To Think About

• In anemia, the reticulocyte count will be abnormal because the levels of red blood cells and hemoglobin are low. Also, reticulocytes make up a higher percentage of the blood count in anemia, which makes the reticulocyte count falsely high. For this reason, a doctor will check the reticulocyte count along with the reticulocyte index (RI) when checking for anemia. The RI is a measurement for reticulocytes when anemia is present.
• A reticulocyte count may help a doctor choose other tests that need to be done to diagnose a specific type of anemia or other disease. A low reticulocyte count may mean a need for a bone marrow biopsy. This can tell if there is a problem with how new reticulocytes are made by the bone marrow. For more information, see the topic Bone Marrow Aspiration and Biopsy.