Drinking large amounts of water or beverages in the morning can have an effect on fasting blood glucose test values. Small amounts of water have little effect on fasting blood glucose. Fasting blood glucose is usually measured early in the morning after 8 to 10 hours of fasting, when fasting blood glucose measurements are more accurate. Drinking small amounts of water in the morning generally has no effect on fasting blood glucose because water does not contain energy; however, drinking large amounts of water, which dilutes the blood, or drinks that contain sugar, can have an effect on blood glucose. Before measuring blood glucose, avoid strenuous activities and mental stress, get enough sleep, and avoid stress. Consult your medical professional for specific precautions.