What It Is

Reticulocytes are immature red blood cells (RBCs). They're made in the bone marrow (the spongy material inside bone) and are released into the bloodstream, where they circulate for about 1-2 days before developing into mature red blood cells. Normally, only about 1% of all RBCs in the bloodstream are reticulocytes.

A reticulocyte count measures the rate at which these cells are made in the bone marrow and enter the bloodstream.

Why It's Done

A reticulocyte count is helpful when a doctor needs more information about someone's anemia (a low number of RBCs). For example, the number of reticulocytes in the blood can be low if anemia is occurring because fewer reticulocytes are being produced by the bone marrow.

The count can be high because more reticulocytes are being produced to replace mature RBCs being destroyed by disease. The test also can be used to monitor whether treatment for anemia is working.

Preparation

No special preparations are needed. Having your child wear a short-sleeve shirt on the day of the test can make things easier for the technician who will be drawing blood.

Let the doctor know if your child has had a blood transfusion in the past 3 months because this can affect the reticulocyte count.

The Procedure

A health professional will usually draw the blood from a vein, after cleaning the skin surface with antiseptic and placing an elastic band (tourniquet) around the upper arm to apply pressure and cause veins to swell with blood. A needle is inserted into a vein (usually in the arm inside of the elbow or on the back of the hand) and blood is withdrawn and collected in a vial or syringe.

After the procedure, the elastic band is removed. Once the blood has been collected, the needle is removed and the area is covered with cotton or a bandage to stop the bleeding. Collecting blood for this test will only take a few minutes.

What to Expect

Collecting a sample of blood is only temporarily uncomfortable and can feel like a quick pinprick. Afterward, there may be some mild bruising, which should go away in a few days.

Getting the Results

The blood sample will be processed by a machine and the results are usually available after a few hours or the next day.

If the reticulocyte count is abnormal, further testing may be necessary to determine what's causing the problem and how to treat it.

Risks

The reticulocyte count is considered a safe procedure. However, as with many medical tests, some problems can occur with having blood drawn:

• fainting or feeling lightheaded
• hematoma (blood accumulating under the skin causing a lump or bruise)
• pain associated with multiple punctures to locate a vein

Helping Your Child

Having a blood test is relatively painless. Still, many children are afraid of needles. Explaining the test in terms your child can understand might help ease some of the fear.

Allow your child to ask the technician any questions he or she might have. Tell your child to try to relax and stay still during the procedure, as tensing muscles and moving can make it harder and more painful to draw blood. It also may help if your child looks away when the needle is being inserted into the skin.

If You Have Questions

If you have questions about the reticulocyte count, speak with your doctor.

Reviewed by: Steven Dowshen, MD
Date reviewed: March 2011