A headache when you sit up is typical of a low cranial pressure headache. The normal intracranial pressure is 80-180 mmH2O. If the intracranial pressure is lower than 60 mmH2O, the patient will have a low cranial pressure headache. When the body sits up, the headache occurs when it loses the fluid cushioning effect of the cerebrospinal fluid and the brain tissue moves mildly downward, stimulating the straining venous sinuses. The headache is relieved when the patient lies flat and mainly manifests as a dull pain. It is necessary to drink more water, which can reach 2000-3000ml per day, to increase the production of cerebrospinal fluid, so that the symptoms of headache can be gradually relieved.