how long is fasting
How Long Should You Fast. Your doctor may recommend a certain time period for fasting; however, the standard amount of time is about eight to 12 hours of no food before having blood drawn. Schedule your blood test for early in the morning so youâll only need to fast overnight to meet requirements. Fast for eight hours before a glucose test. The test is typically conducted in the morning while your body is still in a resting place for a more accurate reading. You must fast at least 12 hours before taking a cholesterol blood test to get an accurate reading on triglycerides.