Your blood is living tissue made up of liquid and solids. The liquid part, called plasma, is made of water, salts and protein. Over half of your blood is plasma. The solid part of your blood contains red blood cells, white blood cells, and platelets. Blood diseases and disorders affect one or more parts of the blood and prevent your blood from doing its job. Many blood diseases and disorders are caused by genes. Other causes include other diseases, side effects of medicines, and a lack of certain nutrients in your diet. Common blood disorders include anemia and bleeding disorders such as hemophilia.