If the patient has sudden dizziness accompanied by fainting: First, it should be considered that it is caused by unstable blood pressure. In case of obvious malignant hypertension, especially when the patient has increased intracranial pressure and hypertensive encephalopathy, there will be sudden dizziness and fainting. Secondly, if various factors lead to dehydration and hypovolemia, there will also be sudden syncope and headache at this time. Third, serious cardiogenic diseases, such as coronary heart disease unstable angina or malignant arrhythmia, heart failure, cardiogenic shock, will also have this clinical symptom. Fourth, for endocrine metabolic diseases, this will also be the case in thyroid dysfunction and adrenal dysfunction. Fifth, if patients with a history of diabetes mellitus have a severe hypoglycemic reaction, they will also have this symptom when their blood sugar is <3.9 mmol/L.