A 24-hour urine collection is a simple lab test that measures what’s in your urine. The test is used to check kidney function. A 24-hour urine collection is done by collecting your urine in a special container over a full 24-hour period. The container must be kept cool until the urine is returned to the lab.
Urine is made up of water and dissolved chemicals, such as sodium and potassium. It also contains urea. This is made when protein breaks down. And it contains creatinine, which is formed from muscle breakdown. Normally, urine contains certain amounts of these waste products. It may be a sign of a certain disease or condition if these amounts are not within a normal range. Or if other substances are present.
A 24-hour urine collection helps diagnose kidney problems. It is often done to see how much creatinine clears through the kidneys. It’s also done to measure protein, hormones, minerals, and other chemical compounds.
Conditions that can cause kidney disease include:
Diabetic nephropathy. This happens when someone has uncontrolled diabetes. It causes high levels of protein (albumin) in the urine and can lead to kidney damage.
High blood pressure. Abnormally high blood pressure can lead to lasting (permanent) kidney damage.
Lupus nephritis. Lupus is an autoimmune disease where the immune system attacks the kidneys and damages them.
Frequent urinary tract infections.
Prolonged urinary tract blockage.
Alport syndrome. This health problem causes vision and hearing problems, as well as progressive scarring of the kidneys. The syndrome is passed down through families.
Nephrotic syndrome. This health problem has several different causes. Symptoms include protein in the urine, low protein in the blood, high cholesterol levels, and tissue swelling.
Polycystic kidney disease. This health problem causes the growth of many fluid-filled cysts in the kidneys. This makes the kidneys larger. Over time, it takes over and destroys working kidney tissue.
Interstitial nephritis or pyelonephritis. This is an inflammation in the small structures in the kidney. It’s often caused by infection.
Screening for preeclampsia in pregnancy. Preeclampsia is a dangerous health problem that sometimes occurs in pregnancy. It causes high blood pressure and can lead to organ failure.
Kidney stones (nephrolithiasis). Kidney stones form because of an imbalance of minerals, salts and water in the urine.
There may be other reasons for your healthcare provider to recommend 24-hour urine collection.
A 24-hour urine collection is a safe, easy test. People can collect urine on their own.
Certain factors may affect the accuracy of a 24-hour urine collection. These include:
Forgetting to collect some of your urine
Going beyond the 24-hour collection period and collecting too much urine
Losing urine from the specimen container through spilling
Not keeping urine cold while collecting it
Certain foods, such as coffee, tea, cocoa, bananas, citrus fruits, and vanilla
There may be other risks depending on your specific health problems. Be sure to discuss any concerns with your healthcare provider before the collection.
Your healthcare provider will explain the procedure and you can ask questions.
Make sure you understand if you need to stay away from certain foods while collecting your urine.
You will be given large containers to store your urine and a container to urinate into. Make sure you know how to use them. Have a cold place to store the urine while you’re collecting it. For instance, a refrigerator or in a cooler on ice.
You may be told to start the collection at a specific time.
If possible, choose a 24-hour period when you will be at home so you do not have to transport your urine.
If you are pregnant or think you may be, tell your healthcare provider.
Make sure your provider has a list of all medicines (prescription and over-the-counter), herbs, vitamins, and supplements that you are taking.
Based on your health condition, your healthcare provider may request other specific preparation.
A 24-hour urine collection may be done on an outpatient basis. This means you go home the same day. Or it may be done during a hospital stay. Procedures may vary depending on your condition and your healthcare provider's practices.
Generally, a 24-hour urine collection follows this process:
You will be given 1 or more containers for collecting and storing your urine. A brown plastic container is typically used. A special pan that fits in the toilet or a urinal may be used to collect the urine. You will need to transfer the urine from the collecting container to the storage container. You will need to keep it cold.
The 24-hour collection may start at any time during the day after you urinate. But your healthcare provider may tell you when to start. It is common to start the collection the first thing in the morning. It is important to collect all urine in the following 24-hour period.
Don't save the urine from your first time urinating. Flush this first specimen, but note the time. This is the start time of the 24-hour collection.
All urine, after the first flushed specimen, must be saved, stored, and kept cold. This means keeping it either on ice or in a refrigerator for the next 24 hours.
Try to urinate again at the same time, 24 hours after the start time, to finish the collection process. If you can’t urinate at this time, it is OK.
Once the urine collection has been completed, the urine containers need to be taken to the lab as soon as possible. If you are doing the urine collection at home, you will be given instructions on how and where to take it.
Depending on your specific health problem, you may be asked to repeat the collection over several days.
There is no special type of care after a 24-hour urine collection. But your healthcare provider may give you other instructions after the procedure, depending on your particular situation.
Before you agree to the test or the procedure make sure you know:
The name of the test or procedure
The reason you are having the test or procedure
What results to expect and what they mean
The risks and benefits of the test or procedure
What the possible side effects or complications are
When and where you are to have the test or procedure
Who will do the test or procedure and what that person’s qualifications are
What would happen if you did not have the test or procedure
Any alternative tests or procedures to think about
When and how will you get the results
Who to call after the test or procedure if you have questions or problems
How much will you have to pay for the test or procedure