Small amounts of water before a patient’s fasting blood glucose test generally have little effect on the results, but sugary drinks are not recommended to avoid affecting the results, and patients who need to measure their fasting blood glucose are advised to consult their doctor. Drinking large amounts of water may dilute the glucose concentration in the blood and cause inaccurate results. If you drink less water, the results are usually not affected. The amount of food a patient has eaten the night before and whether or not he/she has eaten at night may have an effect on the fasting blood glucose test result. Therefore, it is recommended that patients should preferably fast for 8 hours. Meanwhile, patients should eat a light diet and have a regular routine before taking a fasting blood glucose test. When patients need to perform a fasting blood glucose test, it is recommended to follow the doctor’s instructions and strictly implement the fasting requirements under the doctor’s request, so as not to affect the subsequent test.