When your physician orders certain tests, you may need to fast for several hours prior to the test assure accuracy. Nutrients in the foods you eat and beverages you drink can influence test results. For some tests, even the stimulation of digestion enzymes interferes with test results. The amount of time you need to fast can vary between eight and 12 hours. Glucose and cholesterol tests are examples of blood tests that require fasting.
Preparing for Your Test
A fasting blood test requires that you avoid eating or drinking anything except water for a certain period of time before your blood test. This means you won't be able to drink tea until after your blood is drawn. It's best to schedule an early-morning appointment for your blood test so you don't have to go all day without eating. This way, you can sleep through your fast and go directly to your appointment. Take a snack and beverage with you so you can eat and drink as soon as your blood is drawn. If you have questions about your blood test, ask your health care provider.