The younger versions of erythrocytes are called reticulocyte. They are not fully mature. It is one of the stages of erythrocyte development in the bone marrow. They can be released from the bone marrow before they are fully mature in order to increase the number of erythrocytes if needed.

The younger versions of erythrocytes are called reticulocyte. They are not fully mature. It is one of the stages of erythrocyte development in the bone marrow. They can be released from the bone marrow before they are fully mature in order to increase the number of erythrocytes if needed. They are smaller than normal erythrocytes. In order for reticulocytes to mature, they must remain in the bone marrow for 2 days and in the blood circulation for 1 day. If they are released early, the amount of reticulocyte in the blood increases.

In cases such as acute blood loss, increased erythrocyte destruction, where there is a need to increase the reticulocyte level in the blood, the bone marrow tries to meet the erythrocyte requirement by sending the young erythrocytes in its hand to the blood circulation.



In normal blood, 0.5-2% of the cells are reticulocyte cells. Reticulocyte rates may be higher in women or those living at 1800 meters above sea level. The amount of reticulocyte, which is at the level of 2-6% at birth in newborn babies, returns to normal within a few weeks.

In severe anemia, the amount of reticulocyte in the blood increases. This may cause blood hemoglobin or hematocrit levels to be close to normal, resulting in incorrect assessments. The reticulocyte count in the blood should also be evaluated together.

Since the reticulocyte count is expressed as a ratio, reticulocyte levels can be seen as relatively high if there is a decrease in erythrocytes or other cells in the blood. Therefore, it is much more important to examine the reticulocyte count in the blood.

The reticulocyte count in the blood is normally around 30,000-80,000/mm3. The reticulocyte count indicates the production rate of erythrocytes. As erythrocyte production increases, reticulocytes leave the bone marrow earlier.

In the presence of anemia in a patient with a high reticulocyte count, failure of the reticulocyte count to improve after about one week despite treatment indicates severe anemia.

If low reticulocyte count is seen together with anemia, it is an important finding of bone marrow failure.

In cases of sudden bleeding or in cases of hemolysis in which cells die in the vessel, approximately 5-7 days are needed for reticulocytes to enter the circulation.

Different ratios and indices can be used to accurately determine the retilucocyte count and evaluate bone marrow production. For example, “corrected reticulocyte ratio” or “reticulocyte production index” are some of them.



In addition, different calculation techniques related to reticulocyte counts can be used. Some of those:

  • Reticulocyte percentage (RETIC%)
  • Reticulocyte count (RETIC#)
  • Mean reticulocyte volume (MCV r)
  • Mean reticulocyte cellular hemoglobin concentration (CHCM r)
  • Reticulocyte cellular hemoglobin (CH r)
  • Reticulocyte distribution width (RDW r)
  • Width of reticulocyte hemoglobin distribution (HDW r)
  • Reticulocyte cellular hemoglobin distribution width (CHDW r)

The most common causes of reticulocyte increase are:

  • Hereditary spherocytosis
  • Hemolysis
  • Paroxysmal Nocturnal Hemoglobinuria
  • Autoimmune hemolytic anemia
  • Microangiopathic Hemolytic Anemia
  • Hemolytic uremic syndrome
  • Bone marrow diseases

The most common causes of reticulocyte depletion are:

  • Heavy bleeding
  • Severe anemia
  • Diamond-Blackfan anemia,
  • Aplastic crisis
  • Conditions in which the bone marrow is suppressed
  • Bone marrow diseases
  • Leukemias
  • Viral infections
  • Vitamin B12 deficiency
  • Shwachman-Diamond syndrome