Fasting Guidelines for Blood Tests PDF My fasting blood glucose on testing was higher than my post food glucose. Is it abnormal? 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 Glutathione deficiency induces epigenetic alterations of vitamin D metabolism genes in the livers of high fat diet fed obese mice Scientific Reports