The most common way for sugar lovers to understand their blood glucose is fasting blood glucose, postprandial blood glucose and ambulatory blood glucose, so that they can basically have a more comprehensive understanding of their blood glucose level and fluctuations. However, to understand the average level of blood sugar, there is another indicator, which is “glycosylated hemoglobin”. Glycated hemoglobin (GHb) is the product of the combination of hemoglobin in red blood cells and sugar in serum. It is formed through a slow, continuous and irreversible glycation reaction, and its amount depends on the blood glucose concentration and the contact time between blood glucose and hemoglobin, independent of the time of blood sampling, whether the patient is fasting or not, and whether insulin is used or not. Monitoring of glycated hemoglobin gives an idea of the average level of blood glucose in the last three months. Doctors usually recommend checking the glycosylated hemoglobin value every three months or so to know exactly what the blood sugar level has been for the last three months. If it is too high, then even if the fasting blood sugar is normal, it is necessary to consider the regulation of medication, otherwise it may cause complications. Of course, blood glucose monitoring combined with glycosylated hemoglobin testing, sugar lovers can have a very clear understanding of their blood glucose. Only if these indicators can be met can complications be effectively prevented.