The RBC are produced in the bone marrow through a process that takes 7 days called erythropoiesis. This is where the stem cells of hemopoietic differentiate into reticulocytes. Iron, Vit B12 and folic are necessary for hemoglobin synthesis. The reticulocytes become functional RBC after 24 hours in the bloodstream.
After 120 days the RBC are destroyed in the spleen through a process called eryptosis. The heme part is broken down into biliverdin and iron. Iron is recycled by the transferrin while biliverdin is excreted through bile.