Blood sugar fluctuates greatly with fluctuations of hyperglycemia and hypoglycemia. Hyperglycemia may lead to diabetic ketoacidosis and so on, while hypoglycemia may lead to loss of consciousness and so on. 1. Hyperglycemia: blood glucose fluctuation will cause blood glucose to rise too fast, and patients may experience diabetic ketoacidosis and hyperosmolar hyperglycemia syndrome, leading to weakness, drowsiness, and in severe cases, fall into a coma, which is life-threatening. If the patient’s blood sugar fluctuates for a long time, it will damage the retina, blood vessels and nerves, and diabetic retinopathy, diabetic nephropathy and diabetic neuropathy will occur. 2. Hypoglycemia: Hypoglycemia may induce angina pectoris, cerebral infarction and other diseases, causing damage to the cardiovascular system and central nervous system, and severe hypoglycemia can lead to loss of consciousness. If the blood sugar fluctuates greatly, you need to actively consult the doctor and follow the doctor’s instructions for reasonable treatment.