Profound hypoglycaemia is a rare event which has been described in seven cases of anorexia nervosa. A further case is reported here and the literature regarding this complication is reviewed. The major risk factors identified are body weight below 30 kg, a period of fasting and intercurrent infection. Excessive exercise may also play a role. The precise pathogenesis has not been elucidated but several mechanisms, including depletion of liver glycogen, defective gluconeogenesis or failure of glucagon secretion have been proposed. Although hypoglycaemic coma frequently results in death, prompt treatment may result in full recovery as occurred in the case described here.