If headache occurs when not eating, there are usually several factors as follows: 1, the most common factor is the hypoglycemic reaction, when people do not eat belongs to the decomposition of excessive consumption, but not enough income, then there will be a transient hypoglycemic reaction, when the blood glucose is less than 3.9mmol / L will appear around the body serious discomfort, when the blood glucose continues to decrease there will be dizziness accompanied by headache, transient consciousness, not clear, profuse sweating, palpitations, panic, hand tremor and so on. 2, the headache when not eating can also be caused by insufficient cerebrovascular blood supply. Insufficiency, profuse sweating, palpitation, panic, hand tremor, etc. 2, headache without eating can also be caused by insufficient blood supply to the cerebrovascular system, usually in the cerebral blood supply and cerebral vascular ischemia and lack of oxygen, there will be headache, dizziness, and other clinical symptoms and manifestations. 3, endocrine dysfunction and metabolic disorders in patients, the clinical symptoms of headache without eating, such as in the menopause and puberty, this symptom is common in women. This symptom is common during puberty.