Patients with chronic adrenal insufficiency need to adapt their hydrocortisone replacement dose in conditions of physical or psychological stress to prevent life threatening adrenal crisis. In cases of more severe impairment or unsecure gastrointestinal absorption (e.g. gastroenteritis, severe infectious disease), parenteral administration of the hydrocortisone dose is crucial. The study is conducted to offer patients the possibility to perform hydrocortisone self administration in emergency situations in a way of administration which is easy to perform and accepted by the patient. Therefore, pharmacokinetics and safety of subcutaneous hydrocortisone administration will be studied and compared to intramuscular administration.