It is advisable to drink plenty of water when fasting as this hydration makes it easier to draw blood from a vein, as stated by Quest Diagnostics. A person is usually advised not to eat anything for 8 to 12 hours before the test.
Drinking water during fasting will help to make the process of drawing blood go more smoothly. Water helps to enlarge the veins to allow the technician to draw blood easily. A urine test may also be required during the test. Drinking plenty of water will allow the patient to provide a sample easily. Therefore, it is wise to increase water intake the day before the test, as noted by One Medical