A reticulocyte count measures the percentage of reticulocytes (slightly immature red blood cells) in the blood.

A blood sample is needed. For information on how this is done, see: Venipuncture

No special preparation is necessary.

When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.

The test is done to determine if red blood cells are being created in the bone marrow at an appropriate rate. The number of reticulocytes in the blood is a sign of how quickly they are being produced and released by the bone marrow.

The normal range depends on the level of hemoglobin, and the range is higher if there is low hemoglobin due to bleeding or red cell destruction.

Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your doctor about the meaning of your specific test results.

A higher than normal percentage of reticulocytes may indicate:

• Bleeding
• Erythroblastosis fetalis
• Hemolytic anemia
• Kidney disease with increased erythropoietin production

A lower than normal percentage of reticulocytes may indicate:

• Bone marrow failure (for example, from drug toxicity, tumor, or infection)
• Cirrhosis of the liver
• Folate deficiency
• Iron deficiency
• Kidney disease with decreased erythropoietin production
• Radiation therapy
• Vitamin B12 deficiency

Additional conditions under which the test may be performed:

• Anemia of chronic disease
• Congenital spherocytic anemia
• Drug-induced immune hemolytic anemia
• Hemolytic anemia due to G6PD deficiency
• Idiopathic aplastic anemia
• Idiopathic autoimmune hemolytic anemia
• Immune hemolytic anemia
• Pernicious anemia
• Secondary aplastic anemia

There is very little risk involved with having your blood taken. Veins and arteries vary in size from one patient to another and from one side of the body to the other. Taking blood from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight but may include:

• Excessive bleeding
• Fainting or feeling light-headed
• Hematoma (blood accumulating under the skin)
• Infection (a slight risk any time the skin is broken)

The reticulocyte count may be increased during pregnancy.