There is no fasting requirement for a thyroid ultrasound, which means that you can eat before the thyroid ultrasound without any effect. Because the thyroid gland is an organ that is not related to whether or not to eat during the examination, it is not directly related to eating, unlike the examination of the gallbladder and other organs. After a meal when examining the gallbladder, the gallbladder will be emptied and some diseases of the gallbladder cannot be detected well, so fasting is required for liver and gallbladder ultrasound. However, it should be noted that if the thyroid ultrasound reveals abnormalities, thyroid function tests need to be done to match the diagnosis. Fasting is more accurate when blood is drawn for thyroid function tests, so the doctor will generally require fasting when doing thyroid ultrasound, mainly in case there is a problem with the thyroid ultrasound, so that blood tests can be done at once to make an accurate diagnosis.