In its early stages, Addison disease can be hard to diagnose. Diagnosis of Addison disease begins with a medical history and physical exam. Dark tanning of the skin is will often lead the doctor to suspect Addison disease. Blood tests, such as the ACTH stimulation test, can confirm the low cortisol level and its effects on the body. X-ray exams of the adrenal and pituitary glands may be helpful in identifying the cause of the disease.