Headache caused by not eating, usually the following factors: 1, the most common factor is hypoglycemia, in the patient did not eat, it will make the body reserves of glycogen decrease. When the release of glycogen increases, there will be a negative nitrogen balance, which leads to a series of hypoglycemic response, there will be dizziness, headache, weakness and discomfort and other clinical symptoms. 2, headache when eating, but also due to the presence of hypotension. When patients do not eat, the body due to reduced caloric intake, will lead to a significant reduction in blood glucose and blood pressure. When the patient has low blood pressure, it will make the cerebrovascular blood supply is insufficient to lead to headache.3, headache without eating is also related to the spasmodic ischemia of the cerebral arteries. In the cerebral artery spasm, especially the vertebral basilar artery spasm, will produce a transient ischemic reaction, then there will be dizziness, headache and other clinical symptoms.