Addison's disease, also known as primary adrenal insufficiency, is a condition in which the adrenal glands do not produce enough of the hormone cortisol. One of the most common symptoms of Addison's disease is fatigue. Other common symptoms include loss of appetite, weight loss, nausea, muscle weakness, dizziness, low blood pressure, darkening of the skin, and salt cravings. Additionally, people with Addison's disease may experience depression, irritability, and a decreased ability to handle stress. In some cases, people may also experience abdominal pain, low blood sugar, or vomiting. If left untreated, Addison's disease can be life-threatening. It is important to seek medical attention if you experience any of these symptoms.