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Reticulocyte Count
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Lab Tests

Reticulocyte Count

A reticulocyte count measures the number of immature red blood cells in your blood to assess how well your bone marrow is producing red blood cells.

Overview

Reticulocytes are immature red blood cells (RBCs) produced in the bone marrow. They mature into red blood cells within one to two days. The primary function of mature red blood cells is to transport oxygen from the lungs to the rest of the body. A reticulocyte count helps determine if your bone marrow is producing the correct amount of RBCs.

What is it used for?

This test is primarily used to:

  • Diagnose specific types of anemia.
  • Evaluate the effectiveness of anemia treatment.
  • Assess bone marrow function following chemotherapy or a bone marrow transplant.

Why do I need a reticulocyte count?

You may need this test if other blood tests—such as a complete blood count, hemoglobin, or hematocrit—show abnormal results. It is also used if you have symptoms of anemia, including:

  • Shortness of breath
  • Weakness or fatigue
  • Headache
  • Dizziness
  • Arrhythmia

Procedure

For adults, a blood sample is taken from a vein in the arm. For newborns, a provider may perform a heel stick to collect a few drops of blood. No special preparation is required for this test.

Understanding Results

Results are interpreted alongside your medical history and other blood tests.

  • Higher-than-normal count (reticulocytosis): May indicate hemolytic anemia, recent bleeding (hemorrhage), or hemolytic disease of the newborn (HDN).
  • Lower-than-normal count: May indicate iron deficiency anemia, pernicious anemia, aplastic anemia, bone marrow failure, kidney disease, or cirrhosis.

Note that counts may be naturally higher during pregnancy or at high altitudes, and certain medications can influence the results.

Frequently Asked Questions

Your doctor uses the reticulocyte count to gauge how well your bone marrow responds to anemia therapy. A rising count after starting iron, vitamin B12, or erythropoietin indicates a positive response. If the count stays low, the treatment plan may need adjustment—such as changing the medication, checking for absorption problems, or evaluating for bone marrow suppression. Monitoring the count every 2–4 weeks during treatment helps tailor the dose and timing of therapy.
high reticulocyte count (reticulocytosis) usually signals that your bone marrow is working hard to replace red blood cells. Common causes include hemolytic anemia (where red cells are destroyed faster than they are made), recent bleeding, or recovery after blood loss. It can also appear after starting or adjusting anemia treatment. If your count remains high without a clear cause, your doctor may order additional tests such as a peripheral smear, bilirubin levels, or a hemolysis panel to pinpoint the underlying issue.
low count suggests the bone marrow is not producing enough red cells. First, review recent medications, nutritional status, and any chronic illnesses. Your doctor may order iron studies, vitamin B12/folate levels, kidney function tests, or a bone marrow biopsy if a serious marrow disorder is suspected. Addressing underlying deficiencies or treating the root cause often improves the count.
Yes. During pregnancy, the body produces more red blood cells to meet increased oxygen demands, often raising the reticulocyte count. Similarly, at high altitudes, lower oxygen levels stimulate red cell production, leading to a higher count. These changes are normal; however, if the count is unusually high or low for your situation, your clinician may investigate other causes.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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