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The fecal fat test measures the amount of fat in the stool, and the percentage of dietary fat that is not taken in by the body.

Adults and children:

There are many ways to collect the samples. You can catch the stool on plastic wrap that is loosely placed over the toilet bowl and held in place by the toilet seat. Then put the sample in a clean container. One test kit supplies a special toilet tissue that you use to collect the sample, then put the sample in a clean container.

Infants and young children:

For children wearing diapers, you can line the diaper with plastic wrap. If the plastic wrap is positioned properly, you can prevent mixing of urine and stool. Preventing such mixing can give a better sample.

Collect all stool excreted over a period of 24-hours (or sometimes 3 days) in special containers, label the containers with name, time, and date, and send them to the laboratory.

Consume a normal diet containing about 100 grams of fat per day for 3 days before starting the test. The health care provider may advise you to discontinue use of substances that can affect test results, for example, drugs or food additives.

The test involves only normal defecation, and there is no discomfort.

This test is used to evaluate fat absorption as an indication of how the liver, gallbladder, pancreas, and intestines are working.

Fat malabsorption can cause a change in your stools called steatorrhea. Normal fat absorption requires bile from the gallbladder (or liver if the gallbladder has been removed), enzymes from the pancreas, and normal intestines.

Less than 7 grams of fat per 24 hours.

Decreased fat absorption may result from:

• Biliary cancer
• Biliary stricture
• Celiac disease
• Cholelithiasis
• Chronic pancreatitis
• Crohn's disease
• Cystic fibrosis
• Pancreatic cancer
• Pancreatitis
• Radiation enteritis
• Short bowel syndrome (e.g., from surgery or congenital anomaly)
• Sprue
• Whipple's disease

There are no risks.

Factors that interfere with the test are:

• Enemas
• Laxatives
• Mineral oil

Quantitative stool fat determination; Fat absorption

Updated by: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.