Blood is not just the root cause of our existence, it often is an identity; its metaphor can stir up emotions in the most balanced person. Leukemia, a disorder affecting human blood, is the most infamous blood disorder as it has been depicted in many a movie and television series.

A complex mixture of plasma (the liquid component), WBCs (white blood cells), RBCs (red blood cells), and platelets, about 5 to 6 quarts (about 5 liters) of blood is present in the human body. Blood pumped out of the heart takes 20 to 30 seconds to make a complete trip through the circulation and return to the heart.

Blood performs various critical functions as it circulates through the body. It delivers oxygen and essential nutrients including fats, sugars, minerals, and vitamins to the body's tissues. Ferrying carbon dioxide back to the lungs and other waste products to the kidneys for elimination from the body is another key function. Transporting hormones to allow various parts of the body to communicate with each other is the third function. In addition, it also carries components that fight infection and stop bleeding.

An array of reasons can be attributed to blood disorders. The most common are heredity, birth defects, and illnesses. Common blood disorders include coagulopathy, abnormal bleeding, and clotting disorders. Blood disorders often result from defects in the blood vessels or from abnormalities in the blood itself, such as in blood clotting factors or in platelets.

Blood disorders throw the balance maintained by the body off gear and affect the production of blood and its components, such as blood cells, hemoglobin, blood proteins. The mechanism of coagulation also stands to be affected. In people with bleeding disorders, clotting factors are missing or not normal. This causes bleeding for an unacceptable amount of time than people with normal blood clotting behavior.

As a result of the many and complex functions of the blood, there are many disorders that require clinical care by a physician or other healthcare professional. Hematology is the scientific study of blood and blood-forming tissues. A hematologist specializes in the functions and disorders of the blood.