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Fecal fat



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.

Alternative Names

Quantitative stool fat determination; Fat absorption

How the test is performed

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.

How to prepare for the test

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.

How the test will feel

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

Why the test is performed

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.

Normal Values

Less than 7 grams of fat per 24 hours.

What abnormal results mean

Decreased fat absorption may result from:

What the risks are

There are no risks.

Special considerations

Factors that interfere with the test are:

  • Enemas
  • Laxatives
  • Mineral oil

Review Date: 8/8/2008
Reviewed 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.
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