Definition
Reticulocytes are slightly immature red blood cells. A reticulocyte count is a blood test that measures the amount of these cells in the blood.
Alternative Names
Anemia - reticulocyte
How the Test Is Performed
A blood sample is needed.
How to Prepare for the Test
No special preparation is necessary.
How the Test Will Feel
When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or a slight bruise. This soon goes away.
Why the Test Is Performed
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.
Normal Results
A normal result for healthy adults who are not anemic is around 0.5% to 2.5%.
The normal range depends on your level of hemoglobin. Hemoglobin is a protein in red blood cells that carries oxygen. The range is higher if hemoglobin is low, from bleeding or if red cells are destroyed.
Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your health care provider about the meaning of your specific test results.
What Abnormal Results Mean
A higher than normal reticulocytes count may indicate:
- Anemia due to red blood cells being destroyed earlier than normal [hemolytic anemia]
- Bleeding
- Blood disorder in a fetus or newborn [erythroblastosis fetalis]
- Kidney disease, with increased production of a hormone called erythropoietin
A lower than normal reticulocyte count may indicate:
- Bone marrow failure [for example, from a certain drug, tumor, radiation therapy, or infection]
- Cirrhosis of the liver
- Anemia caused by low iron levels, or low levels of vitamin B12 or folate
- Chronic kidney disease
Reticulocyte count may be higher during pregnancy.
Risks
There is little risk involved with having your blood taken. Veins and arteries vary in size from one person 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 lightheaded
- Multiple punctures to locate veins
- Hematoma [blood buildup under the skin]
- Infection [a slight risk any time the skin is broken]
References
Bope ET, Kellerman RD. Hematology. In: Bope ET, Kellerman RD, eds. Conn's Current Therapy 2016. Philadelphia, PA: Elsevier; 2016:chap 12.
Bunn HF. Approach to the anemias. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 25th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 158.
Chernecky CC, Berger BJ. Reticulocyte count – blood. In: Chernecky CC, Berger BJ, eds. Laboratory Tests and Diagnostic Procedures. 6th ed. Philadelphia, PA: Elsevier; 2013:980-981.
A reticulocyte count test measures the number of new red blood cells in your body. It’s sometimes called a reticulocyte index – or “retic count” for short. Doctors use it to help figure out whether you have certain types of
illnesses that affect your blood, such as hemolytic anemia, a condition where red blood cells are destroyed faster than they can be made. Your blood includes many kinds of cells, but red blood cells are the most common. They carry oxygen from your lungs to the rest of
your body. The iron-rich protein called hemoglobin that carries oxygen in the red blood cells is what makes our blood red. Because red blood cells only live about 4 months, your body constantly makes new ones, which are known as reticulocytes. They are bigger than mature red blood cells and are made by bone marrow, a spongy tissue inside many of your bones. When doctors want to know whether your bone marrow is making the right amount of red blood cells, they take a sample
of blood and calculate the number of reticulocytes in it. If you’re like most people, reticulocytes make up about 0.5% to 1.5% of your red blood cells. When you get this test, a lab tech will take a sample of blood from one of your veins. In earlier years, doctors would put a drop of blood on a microscope slide and count the number of reticulocytes themselves. Today, machines calculate the
results of nearly all reticulocyte count tests. A reticulocyte count test is often done when someone is believed to have an illness called anemia, which happens when your body doesn’t make enough red blood cells. That can leave you feeling weak and tired, short of breath, or having
headaches and chest pain. A retic count is often a follow-up to what’s known as a complete blood count or CBC. Most of the
time, the CBC is the first test doctors use to diagnose anemia. There are many different kinds of anemia. If your complete blood count suggests you have anemia, a reticulocyte count is one of several tests that can help tell your doctor which type: What is a Reticulocyte Count Test?
What Happens in a Reticulocyte Count Test?
Why You Might Get One
Other Reasons to Get One
A reticulocyte count test is also useful for people with sickle cell disease. That’s a disorder that makes your body produce red blood cells that are shaped like a crescent, or sickle, instead of being round.
Sickle cells die early and can caught in blood vessels, forming obstructions that cut off circulation to parts of the body. They can cause a form of anemia, because there aren’t enough healthy red blood cells to carry oxygen, as well as other painful or life-threatening illnesses that can put you in the hospital. A high reticulocyte count in someone with sickle cell disease suggests increased hemolysis, and points to a sickle cell crisis. Sickle cell crisis is usually painful and can be life-threatening.
Doctors also use reticulocyte counts when someone has had:
- Chemotherapy or radiation treatment for cancer
- A bone marrow transplant
- Other conditions that can affect production of red blood cells
The tests can tell your doctor whether your bone marrow is starting to recover from the treatment.