A morning fasting blood glucose of 5.3 mmol/L is considered normal, and normal values for fasting blood glucose are usually 3.9 to 6.1 mmol/L. Fasting blood glucose is one of the most commonly used tests for diabetes, and is measured by taking blood before breakfast the next day, after an overnight fast of 8 hours. Fasting blood glucose must be taken after 8 hours of fasting, without taking hypoglycemic drugs or exercising. Fasting blood glucose is generally required to be measured the next day after dinner when no more food has been eaten. If the blood glucose value measured in this case is 5.3 mmol per liter, it means that it is within the normal range and is usually not a big problem. When testing fasting blood glucose, it is important to exclude physiological factors that may cause an increase in blood glucose, such as eating a large amount of sweets, insomnia, emotional excitement, or being under high stress, all of which may lead to transient hyperglycemia. People with abnormal fasting blood glucose are advised to seek prompt medical attention.