how long to fast prior to blood work
Fasting Blood Tests. There are three main tests that require fasting -- glucose, cholesterol and iron. Cholesterol screenings require you to fast for at least 9 to 12 hours prior to blood work, with a 24-hour break from alcohol prior to testing.here are three main tests that require fasting -- glucose, cholesterol and iron. Cholesterol screenings require you to fast for at least 9 to 12 hours prior to blood work, with a 24-hour break from alcohol prior to testing.