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Test ID: NITF Nitrogen, Total, Feces

Reporting Name

Nitrogen, Total, F

Useful For

Determining nitrogen balance, when used in conjunction with 24-hour urine nitrogen measurement


Assessing nutritional status (protein malnutrition)


Evaluating protein catabolism

Clinical Information

Nitrogen is a key component of proteins. Nitrogen balance is the difference between the amount of nitrogen ingested and the amount excreted in the urine and feces. A majority of nitrogen is excreted as urea in the urine; however, fecal nitrogen can account for 30% to 50% of total nitrogen excretion.


A patient who is in negative nitrogen balance is catabolizing muscle protein to meet the metabolic requirements of the protein catabolism and, therefore, urine and fecal nitrogen may be increased due to stress, physical trauma, surgery, infections, burns, and 11-oxysteroid or thyroxine use. Testosterone and growth hormone have anabolic effects on protein synthesis and may decrease urine and fecal nitrogen.


In the course of chronic progressive pancreatitis, as the pancreas is destroyed, serum amylase and lipase may revert to normal. However, excessive fecal nitrogen levels persist and are used as an indicator of pancreatic atrophy.


Average fecal nitrogen (N) excretion is approximately 1 to 2 g N/24 hours. Significantly abnormal excretion rates, resulting in negative nitrogen balance, may be associated with severe stress due to multiple traumas, head injury, sepsis, or extensive burns. Elevated values above 2.5 g N/24 hours may be consistent with chronic progressive pancreatitis. The goal with therapy for a depleted person is a positive nitrogen balance of 4 to 6 g N/24 hours.

Report Available

1 to 8 days

Day(s) Performed


Clinical Reference

1. Morse MH, Haub MD, Evans WJ, Campbell WW: Protein requirement of elderly women: nitrogen balance responses to three levels of protein intake. J Gerontol A Biol Sci Med Sci. 2001 Nov;56(11):M724-730

2. Phinney SD: The assessment of protein nutrition in the hospitalized patient. Clin Lab Med. 1981;1:767-774

3. Konstantinides FN, Kostantinides NN, Li JC, Myaya ME, Cerra FB: Urinary urea nitrogen: too insensitive for calculating nitrogen balance studies in surgical clinical nutrition. J Parenter Enteral Nutr. 1991 Mar-Apr;15(2):189-193

4. Borowitz D, Konstan MW, O'Rourke A, Cohen M, Hendeles L, Murray FT: Coefficients of fat and nitrogen absorption in healthy subjects and individuals with cystic fibrosis. J Pediatr Pharmacol Ther. 2007 Jan-Mar;12(1):47-52. doi: 10.5863/1551-6776-12.1.47

5. Dickerson RN: Nitrogen balance and protein requirements for critically ill older patients. Nutrients. 2016;8(4):226. doi: 10.3390/nu8040226

Method Name

Dumas Combustion

Specimen Type


Shipping Instructions

Send entire stool collection (must contain at least 5 g of feces) frozen on dry ice in Mayo Clinic Laboratories-approved container.

Necessary Information

Length of collection period is required.

Specimen Required

Patient Preparation: Laxatives and enemas should not be used during collection as barium and boric acid interfere with test procedure.

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

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

Specimen Volume: Entire collection (24, 48, 72, or 96 hour)

Collection Instructions:

1. All containers must be sent together.

2. Entire collection must contain at least 5 g of feces.

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

Specimen Stability Information: Frozen 3 years

Additional Information: Patient can store sample at refrigerate temperature during collection period.

Specimen Minimum Volume

See Specimen Required

Specimen Stability Information

Specimen Type Temperature Time Special Container
Fecal Frozen (preferred)
  Ambient  7 days
  Refrigerated  7 days

Reference Values

<16 years: not established

≥16 years: 1-2 g/24 hours

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 US Food and Drug Administration.

CPT Code Information


LOINC Code Information

Test ID Test Order Name Order LOINC Value
NITF Nitrogen, Total, F 16141-4


Result ID Test Result Name Result LOINC Value
17417 Nitrogen, Total, F 16141-4
DUR9 Collection Duration 13363-7
17416 Total Weight 30078-0
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