What Is Reticulocytosis?

Mary McMahon
Mary McMahon

Reticulocytosis is an abnormally large number of immature red blood cells in the circulation. The bone marrow normally produces and releases these cells on a regular basis to replace aging and destroyed cells. Large numbers can indicate that there is a problem with the marrow or the blood, or may be a response to abrupt blood loss. Lab tests can identify the concentration of reticulocytes in the blood and determine if a patient’s blood has other abnormalities, such as low or high numbers of other types of cells.

Red blood cells are produced in bone marrow.
Red blood cells are produced in bone marrow.

In some cases, reticulocytosis may be expected. A patient who has just experienced a hemorrhage should have large numbers of immature cells in circulation because the bone marrow is rushing to replace them. A history of malnutrition can also be a contributing factor. The bone marrow needs a number of nutrients to produce red blood cells, and if it has been deprived, supplementation might cause a spike in reticulocytes as it recovers and starts producing them again.

A reticulocyte count is used to determine if the bone marrow is producing blood cells at a proper rate.
A reticulocyte count is used to determine if the bone marrow is producing blood cells at a proper rate.

It can also be an indicator of a problem in some patients. In hemolytic disorders, the body starts destroying mature, healthy blood cells, which can lead to anemia, where there are not enough red blood cells in circulation to meet the body’s needs. Reticulocytosis may be seen with such disorders as the bone marrow struggles to keep pace with the rate of destruction. Technicians and pathologists evaluating blood from a patient with a suspected hemolytic anemia might expect to find low numbers of mature cells and large numbers of immature ones.

Lab tests can identify the concentration of reticulocytes in the blood.
Lab tests can identify the concentration of reticulocytes in the blood.

The best treatment option for reticulocytosis can depend on why the patient has it. If it is associated with recovery from a condition the patient is already being treated for, a wait and see approach may be advised. Clinicians can request a second blood test to confirm that values are back to normal once the patient has had a chance to stabilize. When it is an indicator of hemolytic anemia or another blood condition, treatment for that condition should resolve the reticulocytosis.

It may be advisable to take the occurrence of a blood transfusion into account when evaluating a patient's blood test results.
It may be advisable to take the occurrence of a blood transfusion into account when evaluating a patient's blood test results.

Patients who have recently had blood transfusions should make sure their care providers are aware of this. The transfusion could skew blood values and might create a false picture. It may be advisable to wait or to take the transfusion into account when evaluating results. Any recent history of massive blood loss can also change the interpretation of results and should be noted in the patient’s chart.

Reticulocytosis is an abnormally large number of immature red blood cells, released into circulation by bone marrow.
Reticulocytosis is an abnormally large number of immature red blood cells, released into circulation by bone marrow.
Reticulocytosis is an abnormally large number of immature red blood cells in the circulation.
Reticulocytosis is an abnormally large number of immature red blood cells in the circulation.
Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a wiseGEEK researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

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