Fasting vs. Non-Fasting Lab Tests A great topic for an Illumination Mobile Phlebotomy educational blog. You can explain the difference in simple, patient-friendly language: Fasting Lab Tests What fasting means before blood work How long patients may need to fast Whether water is allowed What foods and drinks to avoid How coffee, gum, and supplements may affect fasting Tips for making fasting easier What to do if a patient accidentally eats or drinks before the appointment Non