Gastrointestinal (GI) Tests: Types, Preparation and What to Expect
Updated: 2 days ago
Written and medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: November 2026 · How we review
Quick Answer
Gastrointestinal (GI) tests and exams are procedures used to find problems in the esophagus, stomach, small intestine, large intestine and rectum. The three main groups are imaging tests, endoscopy, and lab and functional tests of blood, breath, stool or tissue. Preparation ranges from none to fasting and bowel prep, depending on the test.
What the research says
Screening colonoscopy lowers cancer risk: in a trial of 84,585 people, an invitation to screening colonoscopy lowered the 10-year risk of colorectal cancer from 1.20% to 0.98% (Bretthauer M et al., N Engl J Med, 2022) [2]
Its protection lasts for years: in 88,902 people followed for 22 years, a negative colonoscopy was linked to a 56% lower risk of colorectal cancer, and screening colonoscopy to a 68% lower risk of death from it (Nishihara R et al., N Engl J Med, 2013) [3]
Key takeaways
GI tests check the digestive tract from the esophagus to the rectum.
The main types are imaging, endoscopy and lab or functional tests.
Endoscopy lets doctors see inside and take biopsies.
Preparation can include fasting, a special diet or bowel prep.
Screening colonoscopy helps prevent colorectal cancer.
Types of GI tests
Your provider chooses tests based on your symptoms.
Type | Examples | How it works |
Imaging | Contrast and X-ray video (fluoroscopy) or scans | |
Endoscopy | Upper endoscopy (EGD), colonoscopy, sigmoidoscopy, capsule endoscopy | A camera views the lining; biopsies can be taken |
Lab and functional | H. pylori tests, stool tests, breath tests, gastric emptying study | Samples or measurements of how the gut works |
Sources: [1]
Why they're done
Belly pain, bloating or severe indigestion.
Blood in your stool.
Diarrhea or constipation.
Trouble swallowing or acid reflux.
Vomiting.
Screening for colorectal cancer. Sources: [1]
GI tests can diagnose Barrett's esophagus, GERD, gastritis, H. pylori infection, hiatal hernia, inflammatory bowel disease (IBD), irritable bowel syndrome (IBS), polyps, small intestinal bacterial overgrowth (SIBO), ulcers and tumors. Sources: [1]
How to prepare
Fast, usually starting the night before.
Follow a low-fiber or clear liquid diet if directed.
Complete bowel prep for colon tests.
Stop smoking and temporarily stop certain medicines if asked.
Arrange a ride home if you'll be sedated. Some lab tests need no preparation. Sources: [1]
What to expect
Most tests take a few minutes to an hour.
Imaging: you swallow contrast or receive it by enema while an X-ray video is recorded.
Endoscopy: a lubricated tube with a light and camera is passed through your mouth or rectum; it takes a few minutes to an hour, and biopsies may be taken.
Lab tests: you provide blood, breath, stool or tissue samples. Sources: [1]
Procedure | Sedation |
Upper endoscopy (EGD) | Usually asleep with anesthesia |
Colonoscopy | Anesthesia or conscious sedation |
Sigmoidoscopy, anoscopy, proctoscopy | Usually awake |
Sources: [1]
Risks
Serious complications are uncommon.
A tear in the GI tract.
Reaction to anesthesia.
Bleeding from a biopsy site.
Infection.
Rarely, kidney injury from contrast dye.
Very low radiation exposure from imaging. Sources: [1]
Recovery and results
After sedation, you're monitored and need a driver. You may feel bloating or cramping as air leaves. After contrast imaging, drink plenty of fluids; stool may be white for a few days. Some results are immediate; biopsy results can take several days. Research shows screening colonoscopy lowers the risk of colorectal cancer and related death. Sources: [1, 2, 3]
Conclusion
GI tests give your provider many ways to look at and inside your digestive tract. Choosing the right one depends on your symptoms, and together they can diagnose problems early and prevent cancer.
Keep learning: read about colonoscopy and endoscopy.
Frequently asked questions
What are GI tests?
Tests that check the esophagus, stomach, intestines and rectum.
What are the main types of GI tests?
Imaging, endoscopy and lab or functional tests.
Will I be asleep?
For EGD and often colonoscopy; some tests are done awake.
Do I need bowel prep?
For colon tests, usually yes.
Can I drive afterward?
Not if you were sedated.
Why is my stool white after an imaging test?
From barium contrast; it passes in a few days.
Are GI tests painful?
Most cause little discomfort; sedation is used for some.
What are the risks?
Uncommon problems include tears, bleeding and infection.
When will I get results?
Some right away; biopsies take several days.
Which GI test is used for cancer screening?
Colonoscopy is the most common.
Related Reading
Endoscopy: Types, Preparation, What to Expect and Recovery an overview of endoscopy types.
Colonoscopy: Purpose, Prep, Procedure, Results and Risks a camera exam of the colon.
Upper Endoscopy (EGD): Purpose, Procedure, Preparation and Recovery a camera exam of the upper GI tract.
Upper GI Series: What It Is, Why It's Done, How to Prepare and What to Expect X-ray imaging of the upper GI tract.
Colorectal Cancer Screening: When to Start, Test Options and What Results Mean screening options for colon cancer.
References
Cleveland Clinic. Gastrointestinal (GI) Tests & Exams. Cleveland Clinic. Last updated September 30, 2026. https://my.clevelandclinic.org/health/diagnostics/22018-gastrointestinal-gi-exams
Bretthauer M, Løberg M, Wieszczy P, et al. Effect of colonoscopy screening on risks of colorectal cancer and related death. N Engl J Med. 2022;387(17):1547-1556. PMID 36214590. https://doi.org/10.1056/NEJMoa2208375
Nishihara R, Wu K, Lochhead P, et al. Long-term colorectal-cancer incidence and mortality after lower endoscopy. N Engl J Med. 2013;369(12):1095-1105. PMID 24047059. https://doi.org/10.1056/NEJMoa1301969
Medical disclaimer
This article is for general education only and does not replace advice from a qualified healthcare professional. Talk to your doctor about your own diagnosis and treatment, and seek emergency care right away for severe or sudden symptoms.
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