Yes, it is allowed and actually recommended to drink plain water before fasting blood work. When fasting for blood tests, you should avoid all food and drinks except water for typically 8-12 hours before the test. Drinking water helps keep you hydrated, which can make it easier to draw blood and does not affect the test results. However, you should avoid any other beverages, including coffee, tea, juice, or flavored water, as they can impact the test results. This practice ensures accurate measurements of substances in your blood without interference from recent food or drink intake.