reticulocyte count

What is a reticulocyte count?

Reticulocytes are red blood cells that are still developing. They are also known as immature red blood cells. Reticulocytes are made in the bone marrow and sent into the bloodstream. About two days after they form, they develop into mature red blood cells. These red blood cells move oxygen from your lungs to every cell in your body.

A reticulocyte count (retic count) measures the number of reticulocytes in the blood. If the count is too high or too low, it can mean a serious health problem, including anemia and disorders of the bone marrow, liver, and kidneys.

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

What is it used for?

A reticulocyte count is most often used to:

  • Diagnose specific types of anemia. Anemia is a condition in which your blood has a lower than normal amount of red blood cells. There are several different forms and causes of anemia.
  • See if treatment for anemia is working
  • See if bone marrow is producing the right amount of 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. These include:

  • Fatigue
  • Weakness
  • Shortness of breath
  • Pale skin
  • Cold hands and/or feet

Sometimes new babies are tested for a condition called hemolytic disease of the newborn. This condition happens when a mother’s blood is not compatible with her unborn baby. This is known as Rh incompatibility. It causes the mother’s immune system to attack the baby’s red blood cells. Most pregnant women are tested for Rh incompatibility as part of routine prenatal screening.

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? 

After 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?

If your results show a higher than normal amount of reticulocytes (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.
  • Your baby has hemolytic disease of the newborn, 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 amount of reticulocytes, it may mean you have:

  • Iron deficiency anemia, a type of anemia that happens when you don’t have enough iron in your body.
  • Pernicious anemia, a type of anemia caused by 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, a type of anemia that 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, scarring of the liver

These test results are often compared with results of other blood tests. If you have questions about your results or your child’s results, talk to your health care provider.