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Urinalysis
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Pending specialist review and validation.
The 24 hour urine nitrogen test measures the total amount of nitrogen your kidneys excrete in a full day of urine collection. Nitrogen comes mainly from the breakdown of protein in food and from the normal turnover of body tissues. Because most nitrogen leaves the body in urine, this test offers a practical snapshot of your overall protein metabolism.
Clinicians use this measurement to estimate dietary protein intake and to assess nitrogen balance, especially when you are ill, recovering from surgery, or receiving nutrition support. The result reflects nitrogen from urea as well as other nitrogen containing compounds, so it captures more than a single analyte.
This test helps your care team judge whether you are getting enough protein, too little, or more than your body needs. It is commonly ordered when there are concerns about malnutrition, unintended weight loss, wounds that require protein for healing, or conditions that increase protein breakdown such as severe infection, trauma, or burns. It is also used to monitor the effectiveness of tube feeding or parenteral nutrition.
Kidney and liver function can influence how nitrogen is processed and excreted. Your clinician may pair this test with other labs and a careful diet history to guide nutrition prescriptions and to reduce risks such as muscle loss, poor wound healing, and prolonged recovery.
Interpreting the result starts with confirming a complete and accurate 24 hour collection. Missing any urine or collecting for the wrong time can make the value appear lower or higher than it truly is. Your team may check urine creatinine from the same collection to assess completeness.
A higher than expected result can be seen with high protein intake or when the body is breaking down more tissue than usual. A lower result can occur with low protein intake, poor absorption, or reduced kidney excretion. Liver problems that impair urea production may also lower urinary nitrogen. If your result is outside the expected range, your clinician may adjust your diet, repeat the test, or order additional studies such as kidney and liver panels to clarify the cause.
Reference intervals vary by laboratory, analyzer, methodology, population, and units. The ranges shown here are for education only. Always interpret your results against the reference interval printed on your own lab report.
Missing any urine, starting late, stopping early, or spilling the container will usually make the result falsely low. Carefully follow the collection instructions and record start and stop times.
Higher protein intake, protein shakes, amino acid supplements, or high nitrogen tube feeds increase urinary nitrogen. Very low intake or poor appetite can lower the result.
Fever, infection, trauma, surgery, burns, and hyperthyroidism increase tissue breakdown and raise urinary nitrogen. Corticosteroids can increase catabolism, while anabolic agents may lower excretion.
Reduced kidney function or very low urine output can decrease nitrogen excretion, while high urine output may dilute other markers but not the total amount collected. Results must be interpreted alongside kidney tests.
The liver converts ammonia to urea. Liver disease that impairs this process can lower urinary nitrogen even when protein breakdown is increased.
Fluid intake and diuretic use change urine volume and timing of excretion. Complete the full collection period and avoid missing any voids to keep the result accurate.
Pregnancy, rapid growth, and advanced age can alter protein needs and nitrogen handling. Your provider may use different targets or repeat testing in these situations.
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