An upper GI series is an imaging test that uses X-rays and a drinkable contrast liquid called barium to produce detailed pictures of your esophagus, stomach, and the first part of your small intestine (the duodenum). The test relies on a technology called fluoroscopy, which captures moving X-ray images in real time, letting a radiologist watch the barium travel through your digestive tract and spot problems along the way.
Unlike a standard X-ray that produces a single snapshot, fluoroscopy works more like a video. Barium is a thick, white, chalky substance that coats the lining of your digestive organs, making them stand out clearly on the screen. It isn’t absorbed by your body and passes through your system entirely.
What an Upper GI Series Can Detect
The test is designed to reveal both structural and functional problems in the upper digestive tract. Because the radiologist watches the barium move in real time, they can see not just what your organs look like but how they’re working, including how well you swallow and how food moves from one area to the next.
Conditions commonly identified on an upper GI series include:
- Ulcers in the stomach or duodenum, which appear as craters where barium pools
- Hiatal hernias, where part of the stomach pushes upward through the diaphragm
- Strictures, or abnormal narrowing of the esophagus or stomach outlet
- Tumors and polyps, both benign and cancerous growths
- Diverticula, small pouches that form in the wall of the digestive tract
- Swallowing difficulties, including coordination problems in the esophagus
- Inflammation of the esophagus or stomach lining
How the Procedure Works
You’ll be asked to drink 16 to 20 ounces of the barium solution, which has a milkshake-like consistency. Most people describe the taste as chalky. As you drink, the radiologist begins watching the barium on a fluoroscopy monitor, tracking how it moves through your esophagus and into your stomach.
You’ll then lie on an X-ray table, and the radiologist will ask you to shift into different positions, sitting, standing, and lying at various angles. These position changes help the barium coat all surfaces of your digestive organs so nothing is hidden. The radiologist captures still images at key moments while also watching the live feed. A standard upper GI series typically takes about 30 minutes to an hour.
Small Bowel Follow-Through
Sometimes your doctor will order an extended version of the test called a small bowel follow-through. This tracks the barium beyond the duodenum and through the rest of the small intestine. Because the small intestine is long and the barium moves through it slowly, this version of the test can take around 3 hours and sometimes as long as 6. You may receive an injection that temporarily slows intestinal muscle movement, giving the radiologist clearer images. This extension is useful for detecting problems like Crohn’s disease, small bowel obstructions, or tumors deeper in the intestine.
How to Prepare
Your stomach and upper digestive tract need to be empty for the images to come out clearly. You’ll typically be asked to fast for at least 8 hours before the test, which usually means nothing to eat or drink after midnight the night before a morning appointment. Smoking and chewing gum can also stimulate stomach activity and are generally restricted during the fasting period.
Let your doctor know about any medications you take, since some may need to be paused or adjusted. This is especially important for drugs that affect stomach acid or digestive motility, as they can change how your organs appear on imaging.
Upper GI Series vs. Endoscopy
An upper GI series and an upper endoscopy (where a flexible camera is passed down your throat) can evaluate many of the same problems, but they work differently and have different strengths. The upper GI series is noninvasive. There’s no sedation, no scope, and no recovery time from anesthesia. You drink the barium, get your images, and leave. That makes it a good option when your doctor needs a broad look at the anatomy and function of your upper digestive tract without putting you under.
An endoscopy, on the other hand, lets a doctor see the tissue surface directly and take biopsies. If there’s concern about cancer, bleeding, or a condition that requires a tissue sample to confirm, an endoscopy is usually the better choice. In practice, the two tests are complementary. An upper GI series is often ordered first when symptoms are vague, such as persistent heartburn, unexplained nausea, or difficulty swallowing, and an endoscopy follows if something suspicious turns up.
Barium vs. Water-Soluble Contrast
Barium is the standard contrast for upper GI series because it coats the digestive lining well and produces sharp, detailed images. However, if there’s suspicion that the digestive tract has a tear or perforation, barium can be dangerous. Leaking into the abdominal cavity, it can cause severe inflammation.
In those situations, a water-soluble iodine-based contrast is used instead because it’s safely absorbed by the body if it leaks. The tradeoff is image quality. Water-soluble contrast produces less detailed images and can sometimes miss small tears that barium would reveal. If the initial water-soluble study looks normal but suspicion remains high, a follow-up with barium may still be needed to pinpoint the exact location and size of a perforation.
Radiation Exposure
An upper GI series does involve radiation, but the dose is relatively modest. Studies in adults place the typical effective dose in the range of 2 to 6 millisieverts (mSv). For context, the average American receives about 3 mSv per year from natural background radiation alone, from sources like radon gas and cosmic rays. The dose from a single upper GI series is comparable to roughly one to two years of that natural exposure. It’s a meaningful amount, which is why the test isn’t ordered casually, but it’s well within the range considered acceptable when there’s a clear diagnostic reason.
What to Expect Afterward
There’s no recovery period. You can eat, drink, and resume normal activities right away. The main thing to know about is the barium working its way out. Your stools will appear white or light-colored for a day or two, sometimes up to three days. This is completely normal and simply means the barium is clearing your system.
Barium can cause constipation, so drinking extra water in the days following the test helps move it through. Some facilities recommend a mild laxative if you’re prone to constipation. If you notice that you haven’t had a bowel movement for several days after the test, or if you develop abdominal pain or bloating, contact your doctor, as retained barium can occasionally cause a blockage.
Results are typically read by the radiologist within a day or two and sent to the doctor who ordered the test. If the barium revealed an abnormality, your doctor will discuss next steps, which might include additional imaging, an endoscopy for a closer look, or a referral to a gastroenterologist.