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Test Code FATF Fat, Feces

Reporting Name

Fat, F

Useful For

Diagnosing fat malabsorption due to pancreatic or intestinal disorders


Monitoring effectiveness of enzyme supplementation in certain malabsorption disorders


This test is not useful for differentiating among pancreatic diseases.

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Specimen Type


Necessary Information

Length of collection period is required.

Specimen Required

Patient Preparation:

1. For 3 days prior to and during the collection period:

a. Patient should be on a fat-controlled diet (100-150 g fat per day).

b. No laxatives (particularly mineral oil and castor oil).

c. No synthetic fat substitutes (eg, Olestra) or fat-blocking nutritional supplements.

2. The use of diaper rash ointments will falsely elevate test results. Discontinue use during collection period.

3. Barium interferes with test procedure; a waiting period of 48 hours before stool collection analysis is recommended.

Supplies: Stool Containers - 24, 48, 72 Hour Kit (T291)

Container/Tube: Stool container complies with shipping requirements, do not use other containers.

Specimen Volume:

Preferred: Entire 48-, or 72-hour collection

Acceptable: Entire 24-hour or random collection

Collection Instructions:

1. All containers must be sent together.

2. The entire collection must contain at least 5 g of feces.

3. For a random collection, a minimum of 5 g (do not send entire collection) is required.

4. The number of containers sent should be indicated on the labels (1 of 4, for example).

Additional Information:

1. Patient can store sample at refrigerate temperature during collection period.

2. A separate order and collection should take place if stool bicarbonate, calcium, chloride, magnesium, osmolality, pH, potassium, sodium, or any microbiology testing is desired.

Specimen Minimum Volume

See Specimen Required

Specimen Stability Information

Specimen Type Temperature Time Special Container
Fecal Frozen (preferred) 180 days
  Refrigerated  180 days

Reference Values


≥18 years: 2-7 g fat/24 hours

Reference values have not been established for patients who are <18 years of age.



All ages: 0-19% fat

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

CPT Code Information


LOINC Code Information

Test ID Test Order Name Order LOINC Value
FATF Fat, F 16142-2


Result ID Test Result Name Result LOINC Value
STWT Total Weight 30078-0
DUR2 Duration 13363-7
PFAT Percent Fat 35745-9
TFAT Total Fecal Fat/24 Hr 16142-2

Clinical Reference

1. Van de Kamer JH: Total Fatty Acids in Stool. In: Seligson D, ed. Standard Methods of Clinical Chemistry. Vol 2. Academic Press; 1958:34-38

2. Ellefson RD, Caraway WT: Lipids and Lipoproteins. In: Tietz NW, ed. Fundamentals of Clinical Chemistry. 2nd ed. WB Saunders Co; 1976:474-541

3. Shils ME, Ross AC, Caballero B, Cousins RJ, eds: Modern Nutrition in Health and Disease.10th ed. Lippincott Williams and Wilkins; 2006:1143-1151

4. Shils ME, Ross AC, Caballero B, Cousins RJ, eds: Modern Nutrition in Health and Disease.10th edition. Lippincott Williams and Wilkins; 2006:1227-1234

5. Hart PA, Conwell DL: Diagnosis of exocrine pancreatic insufficiency. Curr Treat Options Gastroenterol. 2015 Sep;13:347-353. doi:10.1007/s11938-015-0057-8

Method Description

After the well-homogenized stool sample is weighed and dried, it is rolled in Teflon and placed in a nuclear magnetic resonance spectrometer (NMR). The NMR determines the percent of fat in the sample. The percent is then converted to grams fat/24 hours excretion or percent fat of random sample.(Korpi-Steiner NL, Ward JN, Kumar V, McConnell JP: Comparative analysis of fecal fat quantitation via nuclear magnetic resonance spectroscopy [1H NMR] and gravimetry. Clin Chim Acta. 2009 Feb;400[1-2]:33-36)

Reject Due To

Preservative, media, or charcoal Reject

Method Name

Nuclear Magnetic Resonance (NMR) Spectroscopy


If not ordering electronically, complete, print, and send a Gastroenterology and Hepatology Client Test Request (T728) with the specimen.

Secondary ID