The person swallows a barium mixture. Barium is a white, chalky substance that shows the digestive tract in clear contrast on x-ray. As the barium moves down, fluoroscopy shows the outlines of the organs and their movements. Fluoroscopy uses x-rays to show movement.
Examiners also take still x-rays to record findings.
It can also aid the diagnosis of absorption and digestive movement disorders. The person eats light meals for 2 or 3 days prior to the test. Fasting and no smoking are required after midnight before the test. The person must also stop many types of oral drugs and antacids. An upper GI series can last up to 6 hours.