Blood Plasma Quality Control by Plasma Glutathione Status Glutathione Index Which blood tests can be done without fasting? HealthcareOnTime Fasting for a blood test typically involves abstaining from food and sometimes drinks for a certain period of time before the test. This is important because eating or drinking can affect the Dietary Supplements Potentially Target Plasma Glutathione Levels to Improve Cardiometabolic Health in Patients with Diabetes Mellitus: A Systematic Review of Randomized Clinical Trials