What is a reticulocyte count?

A reticulocyte count (retic count) measures the number of reticulocytes in your blood. Reticulocytes are immature (still developing) red blood cells (RBCs). Your body makes reticulocytes in your bone marrow. Then it sends them into your blood, where they mature into red blood cells within one to two days. The main job of the red blood cells is to move oxygen from your lungs to every cell in your body.

Your bone marrow constantly creates new red blood cells as your body needs them. A reticulocyte count checks to see if your bone marrow is making the right amount of red blood cells when old ones die off. If you have too few, your tissues may not get enough oxygen. If you have too many, you could be at risk for blood clots or other health concerns. This test can check for certain health conditions or show how well a treatment is working.

If the reticulocyte count is too high or too low, it can be a sign of a serious health condition, including anemia and conditions of the bone marrow, liver, and kidneys.

Other names: retic count, reticulocyte percent, reticulocyte index, corrected reticulocyte, reticulocyte production index, RPI

What is it used for?

A reticulocyte count is most often used to:

• Diagnose specific types of anemia (a condition in which your blood has a lower-than-normal amount of red blood cells)
• See if treatment for anemia is working
• See if bone marrow is producing the right amount of red blood cells
• Check bone marrow function after chemotherapy or a bone marrow transplant

Why do I need a reticulocyte count?

You may need this test if:

• Other blood tests show your red blood cell levels are not normal. These tests may include a complete blood count, hemoglobin test, and/or hematocrit test.
• You are being treated with radiation or chemotherapy.
• You recently received a bone marrow transplant.

You may also need this test if you have symptoms of anemia. They include:

• Shortness of breath
• Weakness or fatigue
• Headache
• Dizziness
• Arrhythmia (a problem with the rate or rhythm of your heartbeat)

Sometimes newborn babies may have a reticulocyte count test to check for a blood disorder called hemolytic disease of the newborn (HDN). This condition may happen if your blood does not match the blood type of your unborn baby. This is known as Rh incompatibility. It causes your immune system to attack your baby's red blood cells.

You most likely will be tested for Rh incompatibility during a routine prenatal screening. This screening helps to prevent HDN by providing early treatment.

What happens during a reticulocyte count?

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 usually takes less than five minutes.

To test a newborn, a health care provider will clean your baby's heel with alcohol and poke the heel with a small needle. The provider will collect a few drops of blood and put a bandage on the site.

Will I need to do anything to prepare for the test?

You don't need any special preparations for a reticulocyte count test.

Are there any risks to the test?

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

There is very little risk to your baby with a needle stick test. Your baby may feel a little pinch when the heel is poked, and a small bruise may form at the site. This should go away quickly.

What do the results mean?

To understand the results of a reticulocyte count test, your provider will consider your symptoms, medical history, and the results of other blood tests.

If your results show a higher-than-normal reticulocyte count (reticulocytosis), it may mean:

• You have hemolytic anemia, a type of anemia in which red blood cells are destroyed faster than the bone marrow can replace them.
• You have had new or ongoing bleeding (hemorrhage), and your body is making many more red blood cells to replace what you've lost.
• Your baby has hemolytic disease of the newborn (HDN), a condition that limits the ability of a baby's blood to carry oxygen to organs and tissues.

If your results show a lower-than-normal reticulocyte count, it may mean you have:

• Iron deficiency anemia, the most common type of anemia. It happens when you don't have enough iron in your body.
• Pernicious anemia, a type of megaloblastic anemia which can happen when your body is not getting enough of certain B vitamins (B12 and folate) in your diet or when your body can't absorb enough B vitamins.
• Aplastic anemia, an uncommon type of anemia, happens when the bone marrow isn't able to make enough blood cells.
• Bone marrow failure, which may be caused by an infection or cancer.
• Kidney disease.
• Cirrhosis, or scarring of the liver.

If your reticulocyte test results were not normal, it doesn't always mean you have anemia or another health condition. For example, your reticulocyte count may not be normal because:

• Your reticulocyte counts may be higher during pregnancy.
• You may have an increase in your count for a short time if you move to a place with a high altitude. The count should return to normal once your body gets used to the lower oxygen levels that happen in higher altitudes.
• Some medicines may increase or decrease your reticulocyte count.

If you have questions about your results or your child's results, talk to your health care provider.

Learn more about laboratory tests, reference ranges, and understanding results.