Fasting Before Blood Tests: When It's Required and Why Lists of Blood Tests That Require Fasting Blood Plasma Quality Control by Plasma Glutathione Status Fasting for Blood Test: How Many Hours Do You Really Need? Fasting for blood work typically involves avoiding food and drink (except water) for eight to twelve hours to ensure accurate results, particularly for tests like glucose, cholesterol, and triglycerides. It is important Which blood tests can be done without fasting? HealthcareOnTime