Dizziness is a typical clinical symptom, which will be present in both hypotension and hypoglycemia. Especially for patients with previous history of diabetes, if blood glucose is lower than 3.9 mmol/L, there will be obvious symptoms of dizziness, patients will have dizziness, headache, weakness of limbs, accompanied by palpitations and a lot of cold sweat. If the blood sugar is further reduced, hypoglycemic coma will also occur. For patients with previous history of hypertension, if they take too much antihypertensive drugs or use the drugs incorrectly, they may also have hypotensive reactions. At this time, patients may suffer from insufficient blood supply to the cerebral arteries, ischemia and hypoxia of brain cells, resulting in dizziness and headache, accompanied by nausea, vomiting and transient syncope.