Mobile Site ›
Print Friendly View

Test ID: NITF    
Nitrogen, Total, Feces


Assessing nutritional status (protein malnutrition)


Evaluating protein catabolism


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




Nitrogen is a key component of proteins. During protein catabolism (proteolysis), nitrogen is excreted in the urine and feces. Protein catabolism may be increased after stress (eg, physical trauma, surgery, infections, burns).


"Nitrogen balance" is the difference between the amount of nitrogen ingested and the amount excreted. A patient who is in negative nitrogen balance is using muscle protein to meet the metabolic requirements of the body and is, therefore, in a catabolic state.


<16 years: not established

> or =16 years: 1-2 g/24 hours

Interpretation Provides information to assist in interpretation of the test results

Average fecal nitrogen excretion is approximately 2 g/day, but fecal nitrogen excretion is highly variable, especially in conditions resulting in excessive protein catabolism. Significantly abnormal excretion rates, resulting in negative nitrogen balance, may be associated with severe stress due to multiple trauma, head injury, sepsis, or extensive burns. Elevated values >2.5 g total fecal nitrogen/24 hours are usually found in cases of chronic progressive pancreatitis. The goal with therapy for a depleted person is a positive nitrogen balance of 4 to 6 g nitrogen/24-hours.


Send ENTIRE STOOL COLLECTION (must contain at least 5 g of feces) frozen on dry ice in Mayo Medical Laboratories approved container.


Measurement of both urine and fecal nitrogen is necessary for the accurate determination of nitrogen balance.


Specify length of collection period and total weight of entire stool specimen.


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

2. Veldee MS: Nutritional assessment, therapy, and monitoring. In Tietz Textbook of Clinical Chemistry. Third edition. Edited by CA Burtis, ER Ashwood: Philadelphia, WB Sanders Company, 1999; pp 1385-1386

3. Konstantinides FN, Kostantinides NN, Li JC, et al: Urinary urea nitrogen: too insensitive for calculating nitrogen balance studies in surgical clinical nutrition. J Parenter Enteral Nutr 1991;15:189-193
