Hypoglycemia is a clinical syndrome triggered by multiple causes, and can occur in diabetic or non-diabetic patients with different etiologies. Most hypoglycemia in non-diabetic patients is mostly caused by drug abuse or other diseases, while hypoglycemia in diabetic patients is mainly caused by impaired blood glucose regulation or improper treatment. Symptoms of hypoglycemia come from two main sources: symptoms of autonomic nervous system hypoglycemia and symptoms of neuronal hypoglycemia in the brain. Autonomic nervous system hypoglycemia symptoms include tremor, palpitations, and anxiety, as well as sweating, hunger, and abnormal sensations. Symptoms of neuronal hypoglycemia in the brain include cognitive impairment, behavioral changes, psychomotor abnormalities, and seizures and coma at even lower blood glucose concentrations. Pallor and sweating are common signs of hypoglycemia. Heart rate and systolic blood pressure rise, but the rise is not great, and manifestations of autonomic hypoglycemia are often observed, with occasional transient neurological deficits. Permanent neurological damage can be seen in patients with prolonged recurrent hypoglycemia and in patients who fail to correct a single episode of severe hypoglycemia in a timely manner. Most patients with hypoglycemia have mild symptoms, and the symptoms will disappear after correcting the blood glucose level without leaving sequelae, but some patients with long-term recurrent hypoglycemia or severe hypoglycemia not corrected in time may still lead to some serious complications. If the hypoglycemia is very serious and not corrected for a long time, it can cause a large area of brain tissue necrosis and softening, resulting in brain atrophy and dementia. Patients with coronary heart disease often have angina pectoris or even myocardial infarction induced by hypoglycemic episodes. Patients with diabetic neuropathy or old age with weakened response to pain may have painless myocardial infarction, which is easy to be ignored and is one of the important causes of sudden death in diabetic patients. Therefore, although most hypoglycemia does not leave sequelae, but serious cases can still lead to complications, and patients should promptly deal with and find the cause of the disease and prevent it in time.