The urine albumin-creatinine ratio (uACR) test measures the amount of two different substances in your urine - albumin (a protein) and creatinine.
Albumin is an important protein normally found in the blood that serves many roles in the body. These roles include building muscle, repairing tissue, and fighting infection. It is not usually found in the urine.
Creatinine is a waste product that comes from the digestion of protein in your food and the normal breakdown of muscle tissue. It is removed from the body through the kidneys and is expected to be found in the urine.
Healthy kidneys stop most of your albumin from getting through their filters and entering the urine. There should be very little or no albumin in your urine. If your kidneys are damaged, albumin can “leak” through their filters and into your urine. Having albumin in your urine (also known as albuminuria or proteinuria) can be a sign of kidney disease, even if your estimated glomerular filtration rate (eGFR) is above 60 or “normal”.
Source: National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Having albumin in your urine (albuminuria or proteinuria) can be a sign of kidney disease, even if your eGFR is above 60 or "normal".
There are three different types of tests available to test your uACR. The quantitative uACR test is the most preferred initial test for people at high risk for kidney disease because it offers the best balance of precision and convenience.
This test measures the actual amount of albumin and creatinine in your urine sample and reports your results as a number. This test only requires a one-time urine sample, also known as a “spot” urine sample. This test is different than the urinalysis your healthcare provider may perform as part of a routine health check using the dipstick method.
A test strip is inserted into your urine sample and changes color based on how much albumin and/or creatinine may be present. Caution – some test strips only test for albumin or creatinine, not both. This test does not report the exact number for how much of each substance is present. Instead, a healthcare professional compares the change in colors on the test strip to a reference chart to estimate how much albumin and/or creatinine may be present. Like the quantitative uACR test, this test only requires a one-time (“spot”) urine sample.
Your healthcare provider or laboratory staff will provide you with a container to collect all the urine you make over a 24-hour period. You will also need to keep the container in the refrigerator in between collections. After 24 hours is over, you will return the filled container to have it analyzed. This test can be the most accurate way to measure your uACR if done correctly, but it is also the least convenient. It is usually used as a next-step option if abnormal results are found using one of the other testing methods or in less common clinical situations.
The uACR is an important test for identifying kidney damage, in addition to the eGFR test. Albuminuria (having albumin in your urine) increases your risk of kidney failure and cardiovascular disease (heart attack or stroke). It can also decrease your life expectancy if left untreated. Kidney disease usually does not show any symptoms until the later stages of the disease – so it is important to have a uACR test done at least once a year if you have any of these risk factors:
Albuminuria (having albumin in your urine) increases your risk of kidney failure and cardiovascular disease (heart attack or stroke). It can also decrease your life expectancy if left untreated.
There is extremely little risk to having a uACR test, especially since the urine is tested after it has left your body naturally.
Before the test
Ask your health care professional if there are any special instructions to follow.
For tests that require a “spot” urine sample, an early morning sample (at least 4 hours without using the bathroom) is preferred but not required. Make sure to drink enough water the day before the test to avoid dehydration and be prepared to make urine during your appointment.
Avoid intense exercise in the 24 hours before your test - this can cause a temporary increase in your uACR. Similarly, you may need to reschedule your test if you experience any of the following events in the 24 hours before your test as they can also interfere with the test and lead to a false positive result:
Fever and/or infection
Heart failure exacerbation (flare-up)
Urinary tract infection
Urinary or menstrual bleeding
A sudden and dramatic increase in your blood pressure or blood sugar
You may also be asked not to eat any meat the day before the test. There is a possibility that it can increase the level of creatinine in your urine and affect your results, although this is not very common.
During the test
Specific instructions may vary by testing center - be sure to follow the instructions provided to you by your healthcare professional or laboratory staff.
In general, this test uses the “clean catch” method to collecting your urine sample. This method includes the following steps:
Wash your hands with soap and water.
Clean your genital area with a cleansing wipe.
Urinate into the toilet for a few seconds and then stop the flow.
Start urinating again, this time into the container. To avoid contaminating the sample, do not let the inside of the container touch your body.
Collect at least 1-2 ounces (30-60 mL) of urine in the container. Most containers have markings to show you how much is needed and when you can stop.
Finish urinating into the toilet.
Put the cap on the container and return it as instructed.
After the test
There are typically no restrictions after completing this test.
The uACR test checks for how much albumin and creatinine is in your urine sample, and then compares the numbers to each other. You may see many numbers from this test on your lab report – focus on the result that has the word ratio in the name. For example, the name on the report may be “alb/creat ratio”, “albumin/creat ratio”, or “albumin/creat ratio, random urine”.
Your uACR results help describe the degree of albuminuria (proteinuria) you may be experiencing, if any. A lower number is better for this test, ideally lower than 30. A value of 30 or higher suggests you may be at a higher risk for kidney failure, a cardiovascular event (heart attack or stroke), heart failure, and even a shorter life expectancy (early death). The higher your number, the higher your risk.
What to do next with your results depends on what your number is. It’s important to emphasize that this test often needs to be repeated one or more times to confirm the results. Decisions are rarely made based on the results from one sample.