There are many reasons for sudden fainting, which must be analyzed in conjunction with the cause of the patient’s onset, the underlying disease, and the patient’s accompanying symptoms: 1. TIA of the vertebrobasilar system caused by transient cerebral insufficiency of blood supply is seen in patients with cerebral arteriosclerosis and cerebrovascular stenosis, which can be caused by transient impairment of vascular contraction and diastolic function. 2. If the patient has low blood pressure or anemia, when he/she suddenly stands up after sitting or squatting for a long time, it will cause postural hypotension and a transient lack of blood supply to the brain, which may lead to fainting. Loss of consciousness, consider a seizure.