Is Fasting required for an abdominal ultrasound? 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 There is a lot of outdated information online, some recommend fasting from 8 to 12 hours.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 Can I have coffee before an abdominal ultrasound? 25/01/2022 Will an abdominal Ultrasound show ovaries? 25/01/2022 Does gallbladder sludge show up on ultrasound? 25/01/2022