Although the diurnal variation of blood glucose in normal people is affected by many factors, it can be stabilized in the range of 3.9 to 7.8 through the regulation of nerves, endocrine and liver. Both under-eating and/or over-utilization can lead to low blood glucose. Adults without type 2 diabetes with blood glucose below 2.8 mmol/L are said to be hypoglycemic and may cause a variety of uncomfortable symptoms, whereas for diabetics, hypoglycemia is diagnosed when blood glucose is below 3.9 mmol/L. Diabetic patients often have elevated blood sugar, so why do they experience hypoglycemia again? Incorrect eating, exercise and medication can lower blood sugar excessively. Severe hypoglycemia can be life-threatening, so diabetics should not only prevent excessive blood sugar, but also not ignore hypoglycemia. Hypoglycemia can occur at any time, and once hypoglycemia occurs, its consequences will be unimaginable if it is not treated in time. I often encountered in clinical work due to hypoglycemic coma patients, and even some patients with hypoglycemic events too long can not wake up, and ultimately can only be a “vegetable”, the state of life. Therefore, diabetic patients should carry candies, cookies and other food to prevent hypoglycemic episodes and patient help card, in order to facilitate timely rescue.