What is the medical term meaning immature red blood cells?
An immature red blood cell is called a reticulocyte. They are produced in the bone marrow and live for about 120 days as mature red blood cells (erythrocytes).
If they are present in high numbers in the blood it suggests that the body is making new red blood cells at an increased rate, either to replace losses due to bleeding or red cell destruction, or because of a pathological process such as leukemia.
Reticulocytes start off in the hollow area of bones called marrow.