Nowadays, people are living in better conditions and are well fed and clothed, so they are more concerned about their health. Therefore, more and more people realize the importance of regular medical checkups, especially for blood pressure, blood sugar and blood lipids, after all, the “three highs” are rising year by year and have to be prevented. Some people may find that their blood glucose is often high and low when they check their blood glucose, although there is no physical discomfort, but there is still some psychological fear of blood glucose problems. So now we need to understand, blood sugar normal people, blood sugar will be high and low? We know that the normal blood sugar reference value is: First, fasting: 3.61~6.05mmol/L (65~109mg/dl). Second, 2 hours after meal: <7.77 mmol/L (<140 mg/dl). If blood glucose is higher than normal, then it belongs to increased blood glucose, and there are two main reasons: one is physiological, like 1 to 2 hours after meal, after glucose injection, increased secretion of adrenaline during emotional stress, and after adrenaline injection, it will make blood glucose increase temporarily, but it should not exceed 6.05 mmol/L. The other is pathological, like various kinds of diabetes, chronic pancreatitis, myocardial infarction, hyperthyroidism, hyperadrenalism, intracranial hemorrhage, etc. If blood glucose is lower than normal, it is lower blood glucose, and there are two reasons: one is physiological, such as hunger, strenuous exercise, after insulin injection, pregnancy, breastfeeding and after taking hypoglycemic drugs. The other one is pathological, like islet cell tumor, abnormal glucose metabolism, severe liver disease, hypopituitarism, hypoadrenalism, hypothyroidism, long-term malnutrition, and insulin overdose. In other words, people with normal blood glucose are affected by some reasons, which cause high and low blood glucose, but this high and low is within the normal reference range, which is normal. On the contrary, it is pathological if it is higher or lower than the normal reference value of blood glucose.