A Cyclosporine Blood Test is a test to assess the levels of cyclosporine in blood. It is used when adjusting the initial dose, and to ensure that cyclosporine levels stay within an acceptable range. Cyclosporine is an immunosuppressant drug. It is used to prevent organ transplant rejection, most notably of the kidney, heart, and liver. It is also used to treat autoimmune diseases, such as rheumatoid arthritis and Crohn’s disease. Cyclosporine works by preventing T-lymphocytes, a type of specialized white blood cell, from producing interleukin-2 (IL-2). IL-2 causes the growth and division of T-lymphocytes. Thus, by preventing its production, cyclosporine suppresses the immune system.