Ferric hemoglobin is an unstable ferritin polymer with iron-containing brown pigment. Excess free hemoglobin produced by intravascular hemolysis is excreted with the kidneys, producing hemoglobinuria, and a portion of it is reabsorbed and degraded by the renal tubular epithelium to produce iron-containing hemoglobin. Clinically, this is mainly seen in the presence of defects within the red blood cells, such as hereditary spherocytosis, orchioptosis, and paroxysmal sleep hemoglobinuria. Exogenous factors can also cause, like autoimmune and drug induced immune hemolytic anemia, and also marching hemoglobinuria, destruction of red blood cells caused by massive burns, malaria, hemolytic streptococcal infections, hypersplenism, etc.