What is the urine urea nitrogen test?

Your body creates ammonia when it breaks down protein from foods. Ammonia contains nitrogen, which mixes with other elements in your body, including carbon, hydrogen, and oxygen, to form urea. Urea is a waste product that is excreted by the kidneys when you urinate.

The urine urea nitrogen test determines how much urea is in the urine to assess the amount of protein breakdown. The test can help determine how well the kidneys are functioning and whether your intake of protein is too high or low. Additionally, it can help diagnose whether you have a problem with protein digestion or absorption from the gut.

Your doctor will usually recommend a urea test to determine protein levels in the body. The test can determine how much protein you’re eating, and if it’s an adequate amount. In addition, your urea nitrogen levels may rise if you’re going through heart failure or dehydration.

A common test for urea nitrogen is the blood urea nitrogen test, better known as BUN. This article refers to the urine urea nitrogen test, which is performed using a urine sample.

A urea nitrogen test can also:

  • assess how well the kidneys are functioning
  • determine if you have kidney disease
  • monitor your kidney disease
  • help diagnose a number of diseases and disorders that may affect how your kidneys function

The urine urea nitrogen test involves analyzing urine samples that you collect during a specified 24-hour period.

Follow your doctor’s orders about how to collect the sample. Generally, you will maintain normal eating and drinking habits during the collection phase.


Wash your hands carefully before and after collecting each sample. Also, make sure that you cap the containers tightly. Label and return the samples to the doctor as instructed. Samples need to be refrigerated during the 24-hour period.

On the first day of collection, you won’t collect a sample when you first urinate that morning. Note the time, and then collect all urine for the remaining 24 hours.

Once collected, the urine is sent to a laboratory for analysis.

A normal urea level in the urine is 12 to 20 grams over 24 hours. Individual labs may have reference ranges that vary slightly and can be different based on sex or age.

Low levels of urea in the urine may suggest:

High levels of urea in the urine may suggest:

Your doctor will contact you to go over your results once your urine samples have been analyzed. They may need to order more tests or physical exams before they’re able to give you a diagnosis.