Test Catalog

Test ID: NITU    
Nitrogen, Total, 24 Hour, Urine

Useful For Suggests clinical disorders or settings where the test may be helpful

Assessing nutritional status (protein malnutrition)


Assessment of protein nutrition and nitrogen balance in hospitalized patients


Evaluating protein catabolism


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

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

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.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

<16 years: not established

> or =16 years: 4-20 g/24 hours

Interpretation Provides information to assist in interpretation of the test results

Urinary nitrogen excretion levels within the normal range are indicative of adequate nutrition. Slightly abnormal excretion rates may be a result of moderate stress or complications such as infection or trauma. Significantly abnormal excretion rates may be associated with severe stress due to multiple traumas, head injury, sepsis, or extensive burns. The goal with therapy for a depleted person is a positive nitrogen balance of 4 to 6 g nitrogen/24 hours.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

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


During nitrogen balance studies, nitrogen lost from exuding wounds, such as burns, and from copious sputum must be included in the patient's evaluation.


Urine samples with visible blood may exhibit a positive bias for nitrogen due to the contribution of nitrogens present within hemoglobin.

Clinical Reference Recommendations for in-depth reading of a clinical nature

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

Special Instructions Library of PDFs including pertinent information and forms related to the test