What Is a Reticulocyte Count?

Reticulocytes are red blood cells that are not fully matured. A reticulocyte count measures the level of reticulocytes in the blood.

As stem cells in the bone marrow begin to mature, they eventually form reticulocytes, which eventually develop into mature red blood cells. Typically, the majority of red blood cells released into the bloodstream from the bone marrow are mature red blood cells. A small percentage of those (0.8%-2.5%) may be reticulocytes.

Reason for the Test

Red blood cells are made in the bone marrow. Most new red blood cells that leave the marrow are matured. A small amount may leave the marrow as reticulocytes. A reticulocyte count can be done to make sure this process is working as it should. The test may show that your body is having a hard time making red blood cells. It may also show that the marrow is working harder than normal to keep the level of RBCs at the right level.

The test may be done as part of basic blood test or to learn more about an anemia.

Type of Sample Taken

Blood will be taken from a vein in your arm or the back of your wrist.

Prior to Collecting the Sample

There are no special dietary or activity restrictions prior to a reticulocyte count. Certain medications may affect test results. Talk to your doctor about any medications you are currently taking.

During the Sample Collection

You will be asked to sit. An area inside your elbow will be cleaned with an antiseptic wipe. A large band will be tied around your arm. The needle will then be inserted into a vein. A tube will collect the blood from the needle. The band on your arm will be removed. After all the blood is collected, the needle will be removed. Some gauze will be placed over the site to help stop bleeding. You may also be given a bandage to place over the site. The process takes about 5 to 10 minutes.

After Collecting the Sample

After the blood sample is collected, you may need to stay seated for 10 to 15 minutes. If you are lightheaded, you may need to stay seated longer. When you feel better, you can leave.

In some cases, a bit of blood may ooze from the vein beneath the skin and cause a bruise. The risk of bruising can be minimized by placing firm pressure over the puncture site. A bruise will usually resolve in a day or 2.

After the sample has been taken, the following complications may rarely occur at the site of the blood draw:

• Redness
• Swelling
• Persistent bleeding or discharge
• Pain

Call your doctor right away if you experience any of these complications.

Results

Results may take anywhere from several days to several weeks to get back.

More reticulocytes than normal may suggest:

• Recent to blood loss
• Response to treatment of some anemias, such as iron deficiency or pernicious anemias
• Hemolytic anemia—a rapid breakdown of red blood cells
• Erythroblastosis fetalis—a potentially fatal blood disorder in the fetus
• Polycythemia vera

Fewer reticulocytes than normal may suggest:

• Problems in the bone marrow such as tumor, infection, or exposure to toxic substances, including chemotherapy
• Cirrhosis of the liver
• Vitamin B-12, iron, or folate deficiency
• Radiation therapy
• Kidney disease
• Any chronic disease with anemia

Many factors can affect the reliability of lab tests. A test may suggest an illness that actually does not exist. This is called a false positive. A test may also miss an illness that actually does exist. This is called a false negative.

A doctor will consider the results from many tests and your symptoms before making a diagnosis. It is important to discuss these results with your doctor before making any conclusions.