Why Drink Water Before Blood Draw?

It's actually good to drink water before a blood test. It helps keep more fluid in your veins, which can make it easier to draw blood.

How much water should I drink before getting blood drawn?

This is generally the case for blood tests and surgeries. If your phlebotomy specialist says it is OK to drink water before getting blood drawn, try to drink the recommended daily amount of water, which is 64 ounces. Before you donate, drink a glass of water that's about 16 ounces.

Why can't I drink water before blood test?

Why Do I Have to Fast? Nutrients in food and drinks go into your bloodstream and can change things measured by the tests, skewing your results. For instance, if you eat or drink before a fasting blood glucose test, your blood sugar probably will be higher than if you hadn't had anything.