Fasting is generally not required for lung enhancement CT, but is recommended for patients with a potential risk of contrast allergy for about 4-8 hours, and patients should consult with their physician before having lung enhancement CT. Patients undergoing lung enhancement CT require the use of contrast media, which is injected into the patient’s blood vessels and may cause an allergic reaction. If the patient does not fast before the test, vomiting may occur, and in severe cases, choking may result. Therefore, for patients at risk of allergic reaction to contrast media, fasting for about 4 to 8 hours is recommended. It is recommended that patients consult their doctor about the matter before having lung enhancement CT, and if they experience discomfort after the examination, they need to seek medical examination promptly.