If you are having an abdominal ultrasound, you are required to fast for at least 4 hours. There is a lot of outdated information online, some recommend fasting from 8 to 12 hours. You Might Also Like What happens after the examination? 25/01/2022 Does gallbladder sludge show up on ultrasound? 25/01/2022 Can you see cirrhosis on an ultrasound? 25/01/2022 Where can i get an ultrasound in London without doctors referral? 25/01/2022