As we all know, for diabetic patients, scientific selection and reasonable matching of diet is the basis of diabetes treatment, which is an important treatment tool to ensure the blood sugar standard and prevent diabetes-related complications. We often use the method of food exchange to guide diabetic patients on how to choose food, and this classic method has played an important role in blood glucose control. However, its role in diabetic diet education is limited by its inability to distinguish the difference in the magnitude of postprandial glucose elevation caused by calorie equivalent foods in the exchange table. In 1981, Jenkins et al. first proposed the glycemic index (GI) of foods as the physiological basis for the classification of sugary (carbohydrate-containing) foods. The glycemic index is the ability of a food to cause how much a body’s blood glucose can rise, and is a valid physiological parameter for evaluating the postprandial glycemic effect of food. Foods containing carbohydrates can be classified according to their GI values. It is generally considered that a GI value of less than 55 is a low GI food, a GI value of 55-75 is a medium GI food, and a GI value greater than 75 is a high GI food. It is found that high GI food, which is digested quickly and absorbed at a high rate after entering the gastrointestinal tract, raises the postprandial blood sugar to a greater extent; low GI food, which stays in the gastrointestinal tract for a long time and has a low absorption rate, raises the postprandial blood sugar to a lower extent. In addition, the physical state of food also affects its GI. The GI of dry rice and thin porridge made of the same weight of rice has obvious differences. Food in liquid form quickly enters the intestine from the stomach and raises blood sugar very significantly. The introduction of the concept of glycemic index provides a more reliable basis for diabetic patients to choose and reasonably match their diets. When we know the above knowledge of glycemic index, many people will think of a question: since foods with high GI value raise blood sugar more after meal, should these foods be excluded from the diabetic patients’ diet plan? For this reason, a new concept has been introduced in the field of diabetic diet therapy: “glycemic load (GL)”. Glycemic load is the product of the number of carbohydrates in a food and its GI, divided by 100, i.e. GL = (grams of carbohydrates in food x GI)/100 . For example, if the GI of a baked potato is 85, the glycemic load of 40 grams of this carbohydrate consumed is 34. GL combines the quantity and quality of carbohydrates consumed by the body to assess the total glycemic effect of the diet, and discards the one-sidedness of measuring the glycemic effect of food simply by the high or low GI of the food. Therefore, GL is more comprehensive than GI in evaluating the ability of food to cause postprandial blood glucose elevation . Generally speaking, GL value higher than 20 is high glycemic load food, 11-19 is medium glycemic load food, and less than 10 is low glycemic load food. The higher the GL value of a food, the greater the effect of consuming the same weight of food on postprandial blood glucose. So, let’s answer the question we asked before: are foods with high GI values contraindicated in the diet of diabetic patients? The GI value of watermelon is 72, which is a high GI value. 100 grams of watermelon contains 5.5 grams of carbohydrates, so if you eat 100 grams of watermelon, its GL=(72×5.5)/100=3.96. In this way, consuming 100 grams of watermelon at a time has little effect on the blood sugar of diabetic patients. However, if 1000 g of watermelon is consumed at one time, its GL value is 19.8, which has a more significant effect on the postprandial blood glucose of diabetic patients. In addition, the CI of soda crackers is also 72, but it contains about 76 grams of carbohydrate per 100 grams. Consuming 100 grams of soda crackers, its GL = (76 × 72) /100 = 55, which has a significant effect on postprandial blood sugar. However, when we consume only 20 grams of soda crackers, the GL value is about 11, and the effect on blood sugar is minimal. By knowing the GL value we know that diabetic patients are allowed to include high CI foods in their diet plan. In other words, with strict control of food weight, for any food, diabetic patients are allowed to consume. Following the concept of combining GI and GL to select foods and match dietary structure to achieve a balance between quality and quantity of carbohydrates, which is conducive to reducing pancreatic islet cell load, has important clinical significance in effectively controlling and stabilizing blood glucose, reducing diabetes-related complications and improving the quality of life of diabetic patients.