What kind of medicine or treatment does a person with addison's disease have to get?

Cortisol replacement. Hormone replacement therapy is life-saving. Depending on the physician and patient preferences, treatment may be with hydrocortisone, prednisone, or dexamethasone.
Cause. All patients with addison's disease need to take glucocorticoid steroids. Additional treatment may be needed depending on the cause of illness. It may be a part of multiple endocrine failure in which case other hormones supplements will be needed. In any case addison's disease is too serious for self-treatement. Consult your doctor.
Addison's disease. Addison's disease is a disorder that occurs when your body produce insufficient amount of a hormone called cortisol and possibly another called aldosterone. There are many causes for this. You will need blood work and possibly imaging studies to make the diagnosis. The treatment is to replace what is missing: usually a steroid such as prednisone/hydrocortisone and possibly fludrocortisone.