Reticulocyte count
Young red blood cells whose number shows how actively the bone marrow makes new ones
Also known as
Definition
Reticulocytes are immature red blood cells. The bone marrow makes them and releases them into the blood, where they mature into red blood cells within one to two days. Their number in the blood shows how quickly the bone marrow is replacing red blood cells. The value helps classify types of anemia and is used over time to see whether anemia treatment is working. There are also derived measures such as the reticulocyte production index.
| Parameter | Value |
|---|---|
| Unit | % of red blood cells |
| Reference Range | For healthy adults without anemia, MedlinePlus lists about 0.77–2.26%. If hemoglobin is low from blood loss or increased cell breakdown, the expected range is higher. Labs differ and some also report the absolute count; the range printed on your report is what counts. Your doctor interprets the result. |
Agree on your personal target range with your doctor.
↓ What a low value means
A low reticulocyte count can indicate that the bone marrow is making too few red blood cells. Possible links are anemia due to a lack of iron, vitamin B12 or folate, aplastic anemia, bone marrow failure caused for example by medicines, tumors, radiation or infections, chronic kidney disease with too little erythropoietin, and liver cirrhosis. Discuss any deviation with your doctor.
↑ What a high value means
A raised count (reticulocytosis) shows that the bone marrow is stepping up production. This can be related to hemolytic anemia, in which red blood cells are broken down early, to new or ongoing bleeding, or to kidney cysts or tumors that produce extra erythropoietin. Pregnancy, a stay at high altitude and some medicines can also raise the value temporarily. Discuss any deviation with your doctor.
When to test
The test is usually ordered when the blood count, hemoglobin or hematocrit is abnormal, with signs of anemia such as shortness of breath, weakness, fatigue, headache or dizziness, during anemia treatment, and after chemotherapy, radiation or a bone marrow transplant. No special preparation is needed.
Frequently asked questions
Why is the value measured during anemia treatment? +
Reticulocytes show how actively the bone marrow is making new red blood cells. A change over time can therefore indicate whether a treatment is working. How to assess the trend is up to your doctor.
Does an abnormal value always mean anemia? +
No. MedlinePlus lists pregnancy, moving to a high altitude and some medicines as reasons for changed values. Symptoms, medical history and other blood values are taken into account.
What is the difference between reticulocytes and red blood cells? +
Reticulocytes are the precursor: young red blood cells that mature in the blood within one to two days. The red blood cell count describes the existing supply, the reticulocyte count rather the current production.
Do I need to fast for the test? +
No, according to MedlinePlus no special preparation is needed. If other values are measured in the same blood draw, their requirements apply.
Reticulocyte count
Sources
Last updated: October 05, 2026
This information is for orientation only and does not replace medical advice. Reference ranges can vary by laboratory, method and country.