If a person has a headache after waking up, it is usually due to several factors: 1. Insufficient blood supply to the basilar artery due to compression of the cervical spine during sleep, sometimes incorrect posture during sleep can compress the cervical spine, especially sensitive to compression of the 2nd-6th cervical vertebrae, which can lead to insufficient blood supply to the basilar artery and cause symptoms of headache and dizziness due to head ischemia. 2. The headache when waking up is also caused by lack of oxygen. This is because the sleeping environment is confined, narrow or unventilated, and thus there is ischemia and lack of oxygen in the brain, especially when the arterial oxygen saturation and partial pressure of oxygen are insufficient, there will be an imbalance in the ratio of ventilation and blood flow, and this will also lead to headache symptoms. 3, such as hypoxia and ischemia of the large arteries, especially when the coronary arteries are ischemic, insufficient and relatively weakened blood supply, there will also be a headache when waking up. 4, when the blood viscosity increases during sleep and When blood viscosity increases and blood thickening increases during sleep, headache after waking up can also occur.