Does this test have other names?
Fat in stool, fecal fat stain, quantitative stool fat, qualitative stool fat
What is this test?
This test measures the amount of fat in your stool.
Having too much fat in your stool is called steatorrhea. If you have too much fat
in your stool, it may be a sign that food is moving through your digestive system
without being broken down and absorbed correctly. This is called malabsorption. Having
a fecal fat test is the best way to find out if you have malabsorption.
You can develop malabsorption if:
Your intestines don't absorb food
Your pancreas doesn't make enough digestive enzymes
Your liver isn't making enough bile. Your body needs bile to break down fats for digestion.
You can have 2 types of fecal fat tests: qualitative and quantitative. For a qualitative
test, the lab checks a single stool sample under a microscope to count the number
of fat globules, or droplets. For a quantitative test, you collect stool samples usually
over a period of 3 days. These samples are measured to find the total amount of fat
in your stool each day.
Why do I need this test?
You may need this test if you have symptoms of a disease that causes malabsorption.
This test only finds out whether you have malabsorption. It doesn't diagnose a specific
disease. Symptoms of malabsorption include:
Frequent greasy, loose stools in large amounts
Foul-smelling, fatty stools
Unintentional weight loss
You may also have this test if you have already been diagnosed with malabsorption
to see how well your treatment is working.
What other tests might I have along with this test?
Your healthcare provider may also order a D-Xylose absorption test to help figure
out the cause of malabsorption. D-Xylose is a type of sugar. Your provider may also
order imaging tests, such as an upper endoscopy, a colonoscopy, or X-rays, of your
small intestine to find out the cause.
What do my test results mean?
Test results may vary depending on your age, gender, health history, and other things.
Your test results may be different depending on the lab used. They may not mean you
have a problem. Ask your healthcare provider what your test results mean for you.
A qualitative fecal fat test counts the number of fat globules in your stool. This
test measures 2 types of fat globules: neutral fat and fatty acids. Normal results
Results for a quantitative fecal fat test are given in grams per 24 hours (g/24 h).
Normal results are:
2 to 7 g/24 h for adults, with fat being less than 20% of the solid stool sample
Less than 1 g/24 h for a baby:
In bottle-fed babies, fat should make up 30% to 50% of the sample
In breastfed babies, fat should make up 10% to 40% of the sample
If your results are higher, it may mean you have one of these diseases:
Celiac disease (sprue)
Diseases of the pancreas
How is this test done?
This test is done with a stool sample. The method of collecting a stool sample varies
depending on the type of fecal fat test you need. Your healthcare provider will explain
how to collect and store the samples.
Does this test pose any risks?
This test has no known risks.
What might affect my test results?
Your results can be affected by several things. These include:
Using a rectal suppository or oily rectal cream
Swallowing castor oil or mineral oil
Not eating a balanced diet
Eating too much fiber or taking a fiber-based stool softener
Urine in the stool sample
Taking certain medicines, such as orlistat
How do I get ready for this test?
Depending on the type of fecal fat test you are having, you may need to follow a special
diet and not use laxatives. Your healthcare provider will let you know what to do
for this test. You may have to:
Follow a diet that includes 100 to 150 grams of fat, 100 grams of protein, and 180
grams of carbohydrate for 6 days before the test and during the test
Follow a diet that has 100 grams of fat for 3 days
Stop using laxatives before and during the test
Stop eating foods high in fiber
Stop using oily rectal creams or suppositories
Babies and children will need to have a specific amount of fat in their daily diet
before the test.
Be sure your healthcare provider knows about all medicines, herbs, vitamins, and supplements
you are taking. This includes medicines that don’t need a prescription and any illegal
drugs you may use.