If you drink a small amount of pure water before checking your fasting blood glucose, it is OK and will not affect your blood glucose greatly; if you drink a large amount of water or drink sugary water, it is not OK and will affect the test results. Measurement of fasting blood glucose requires fasting for 8 to 10 hours, it is best not to drink water, if there are drugs that must be taken, such as antihypertensive drugs, a small amount of pure water can be used to send to the service, or very thirsty, you can also drink a small amount of water, the impact on the fasting glucose is not very big, you can continue to measure the fasting blood glucose. If you drink a lot of water in the morning, it will lead to blood dilution, which may affect the fasting blood glucose measurement and lead to inaccurate results. If you drink sugary water in the morning, such as beverages, honey water, sugar water, etc., it will have an effect on your fasting blood glucose, leading to inaccurate results. Checking fasting blood glucose should be carefully prepared in strict accordance with the doctor’s recommendations and any abnormalities should be promptly attended to.