Understanding Your Test: What It Is, How It Is Performed, and How to Prepare

This test helps your healthcare provider check how well your body is working and look for signs of a specific condition. It may be ordered to confirm a diagnosis, rule out a possible illness, or monitor how a treatment plan is going over time. Your results are always interpreted together with your symptoms, medical history, and physical exam.

The 24-hour urine ammonia test measures how much ammonia your kidneys excrete in your urine over a 24-hour period. Ammonia is a waste product created when your body breaks down protein. Normally, your liver converts ammonia into urea, which your kidneys filter out and excrete in urine.

The test is usually performed in a doctor's office, clinic, or laboratory by a trained member of your care team. Depending on what your provider has ordered, it may involve collecting a small sample of blood, urine, or another specimen, or a simple imaging step. The appointment itself is typically brief, and most people can return to their normal activities right away.

You will receive a special container from the laboratory. For 24 hours, you will collect all your urine in this container. This includes the first morning urine on day one (which you skip), and includes the first morning urine on day two (which you include). Keep the container refrigerated or in a cool place during the collection period. Return the complete container to the lab as instructed.

Your care team will give you specific instructions before the appointment, so follow them closely. In general, drink plenty of water unless you are told otherwise, keep taking your regular medicines unless your provider says to stop, and mention any allergies or bleeding problems. If fasting is required, you will be told exactly how many hours to avoid food and drink beforehand.

Your healthcare provider may give you specific instructions. Generally, you should avoid strenuous exercise during the collection period. Inform your doctor about all medications, vitamins, and supplements you are taking, as some may affect test results. Follow any dietary instructions provided.