how long do you fast before blood work
What to know about fasting before your lab test. With certain blood tests, you may be instructed to fast for up to eight hours before your appointment. Fasting before a blood draw means you donât eat or drink anything except water. Donât wait until the day of your blood draw to ask if you should fast. That could cause your appointment to be rescheduled. If at any point youâre unsure if fasting is required, contact your doctor. Why do I have to fast before certain lab tests?