Leukemia also known as blood cancer is a malignant disease (cancer) of blood-forming cells in the bone marrow. These deranged, immature cells accumulate within the blood and organs of the body and are unable to carry out the normal functions of blood cells.

The blood is made up of a fluid called plasma and three types of cells, namely white blood cells (WBCs or leukocytes), red blood cells (RBCs or erythrocytes), and platelets (thrombocytes). WBCs helps the body to fight infections and other diseases. RBCs which gives blood its color, carry oxygen from the lungs to the body's tissues and take carbon dioxide from the tissues back to the lungs. Platelets helps to form blood clots that control bleeding. These blood cells are formed in the bone marrow, the soft, spongy center of bones.

Normally, blood cells are produced in an orderly, controlled way as the body needs them. When leukemia develops, the bone marrow produces large numbers of abnormal white blood cells that do not function properly. It also causes low levels of platelets and hemoglobin, which is found inside red blood cells.