A stool analysis is a series of tests done on a stool (feces) sample to help diagnose certain conditions affecting the digestive tract. These conditions can include infection (such as from parasites, viruses, or bacteria), poor nutrient absorption, or cancer.

For a stool analysis, a stool sample is collected in a clean container and then sent to the laboratory. Laboratory analysis includes microscopic examination, chemical tests, and microbiologic tests. The stool will be checked for color, consistency, weight (volume), shape, odor, and the presence of mucus. The stool may be examined for hidden (occult) blood, fat, meat fibers, bile, white blood cells, and sugars called reducing substances. The pH of the stool also may be measured. A stool culture is done to find out if bacteria may be causing an infection.

Why It Is Done

Stool analysis is done to:

• Help identify diseases of the digestive tract, liver, and pancreas. Certain enzymes (such as trypsin or elastase) may be evaluated in the stool to help determine how well the pancreas is functioning.
• Help find the cause of symptoms affecting the digestive tract, including prolonged diarrhea, bloody diarrhea, an increased amount of gas, nausea, vomiting, loss of appetite, bloating, abdominal pain and cramping, and fever.
• Screen for colon cancer by checking for hidden (occult) blood.
• Look for parasites, such as pinworms or Giardia lamblia.
• Look for the cause of an infection, such as bacteria, a fungus, or a virus.
• Check for poor absorption of nutrients by the digestive tract (malabsorption syndrome). For this test, all stool is collected over a 72-hour period and then checked for the fat and meat fibers. This test is called a 72-hour stool collection or quantitative fecal fat test.

Talk to your doctor about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results will indicate. To help you understand the importance of this test, fill out the medical test information form(What is a PDF document?).

How To Prepare

Many medicines can change the results of this test. You will need to avoid certain medications, such as antacids, antidiarrheal medications, antiparasite medications, antibiotics, enemas, and laxatives for 1 to 2 weeks before you have the test. Be sure to tell your doctor about all the nonprescription and prescription medicines you take.

Be sure to tell your doctor if you have:

• Recently had an X-ray test using barium contrast material, such as a barium enema or upper gastrointestinal series (barium swallow). Barium can interfere with test results.
• Traveled in recent weeks or months, especially if you have traveled outside the country. Parasites, fungi, viruses, or bacteria from other countries may affect the test.

If your stool is being tested for blood, you will need to follow a special diet for 2 days before the stool collection period begins. Your doctor will give you a list of recommended foods.

• Do not eat red meat, turnips, cauliflower, broccoli, bananas, cantaloupe, beets, or parsnips.
• Do not drink alcohol, including wine and beer.
• Do not take aspirin, ibuprofen, or vitamin C.