What is a urine 24-hour volume test?
The urine 24-hour volume test measures the amount of urine your body produces in a day and analyses what is in your urine. It’s a noninvasive procedure that involves no pain or discomfort. This simple test typically helps diagnose problems with kidney function.
Your doctor may order this test if they think you might have a kidney disease or if you’re producing abnormally large volumes of urine, a condition called polyuria. Polyuria appears in diabetes insipidus, an uncommon condition that occurs when your kidneys can’t conserve water.
Urine volume is also measured as part of the creatinine clearance test or any other test that measures the amount of a substance eliminated in a 24-hour period.
You might take only this test, or you might take it along with other procedures. This test can help your doctor determine if you have kidney disease.
There’s very little preparation needed for the urine 24-hour volume test. Your doctor may give you more specific instructions depending on your current medical condition and the reasons for the test.
Tell your doctor if you’re pregnant or think you may be pregnant. Be sure to inform your doctor about any current prescription and over-the-counter medications and supplements you’re taking and ask if any of these will interfere with the results.
Typically, you don’t need to fast or take certain medications to prepare. However, based on the reasons for the test, your doctor may advise you to avoid certain foods or beverages during the test.
Because this test involves collecting and storing urine for a 24-hour period, you may want to consider scheduling the test for a day when you’re at home. Ask if you must start the test at a particular time, and adjust your schedule accordingly.
You’ll receive one or more containers for collecting and storing urine. Make sure you understand when and where you should return the container or containers.
The goal is to collect your urine for a 24-hour period. You can do this while you’re in the hospital, but you can also easily do it on an outpatient basis. The test should begin at a specific time and end at the same time on the following day. The test will follow these steps:
- Your test will usually begin in the morning. On the first day, don’t collect your first morning urine, but note and record the time.
- Collect all your urine for the next 24 hours, keeping the storage container refrigerated.
- Collect your first morning urine on the second day at the same time you began the test on the previous day.
- Keep the container cool until it’s time to return it. Make sure the cover on the container is tight, and return it promptly to the lab or your doctor’s office as instructed.
Under some circumstances, your doctor may want you to repeat the procedure several times.
If you’re collecting your baby’s urine, you’ll receive special urine collection bags with adhesive paper to keep them in place. Follow these steps:
- Wash the area around your baby’s urethra, which is the area where urine comes out of their body.
- Place the urine collection bag on your baby. For boys, place their entire penis in the bag. For girls, place the bag over their labia. You may place a diaper over the bag.
- Check the bag frequently, and drain urine from the bag into the urine collection container. Replace the used bag with a clean one.
- Keep the collection container refrigerated until it’s time to return it.
- After the 24-hour period is complete, return the container as instructed by your doctor.
The urine 24-hour volume test is noninvasive, and it only involves urinating as you normally would. There are no side effects or risks.
It’s important to follow instructions to get accurate results. Several factors can affect the accuracy of your test, including:
- failing to collect all your urine in the 24-hour period
- going beyond the 24-hour period and collecting too much urine
- spilling urine from the container
- not keeping the urine cool
- not returning the urine sample promptly
Other factors that may interfere with results include acute stress and vigorous exercise. Let your doctor know if that’s the case for you. Your doctor may want you to repeat the test in some cases.
The normal range of urine output is 800 to 2,000 milliliters per day if you have a normal fluid intake of about 2 liters per day. However, different laboratories may use slightly different values. Your doctor will explain what your particular numbers mean.
Normal urine is sterile and contains no bacteria, viruses, or fungi. Urine is a mixture of water and chemicals, proteins, or electrolytes such as:
- urea, which is formed when protein breaks down
- creatinine, which is formed when muscles break down
- other chemical compounds
Your doctor may want to order additional testing if your urine contains too much or too little of these chemicals. They may also want to order additional tests if your urine output is unusually high or low.
An abnormally low urine volume may indicate:
- inadequate fluid intake
- renal insufficiency
- renal failure
An abnormally high urine volume may indicate:
- renal diabetes insipidus
- central diabetes insipidus
- some forms of kidney failure
- unusually large fluid intake
- use of diuretic medications
Your doctor will explain the results of your test and let you know if you need additional testing.