What Is a Urine Albumin or ACR Test?
A urine albumin test checks whether a protein called albumin is passing into your urine.
Albumin is normally found in your blood. Healthy kidneys keep almost all of it in the bloodstream.
If the kidney filters become damaged, more albumin may pass into the urine. This is called albuminuria.
A common way of measuring this is the urine albumin-to-creatinine ratio, usually called ACR or UACR.
This simple urine test can sometimes show signs of kidney damage even when other kidney results are still relatively normal.
However, one abnormal result does not automatically mean that you have chronic kidney disease. The test may need to be repeated, and your doctor will consider it together with your other results.
What Is Albumin?
Albumin is a protein normally found in your blood.
Your kidneys filter your blood to remove waste and excess water while keeping useful substances in the bloodstream.
Healthy kidneys normally allow only a very small amount of albumin to enter the urine.
If more albumin starts appearing in the urine, it can be a sign that the kidney filters have been affected.
What Does Albuminuria Mean?
Albuminuria simply means that there is more albumin in the urine than expected.
It can be an early sign of kidney damage.
This does not mean that everyone with one abnormal urine albumin result has chronic kidney disease.
Doctors look at:
- how high the result is;
- whether it remains high when the test is repeated;
- your other kidney tests;
- your medical history.
What Does “Microalbumin” Mean?
You may see terms such as:
- urine microalbumin;
- microalbumin test;
- microalbuminuria.
These are older terms that are still commonly used.
The word microalbumin does not mean that there is a special smaller type of albumin.
It refers to testing for relatively small increases in albumin in the urine.
Today, the result is commonly described as albuminuria and measured using the albumin-to-creatinine ratio (ACR).
So if your doctor or laboratory asks for a “urine microalbumin” test, it is usually part of checking for increased albumin in your urine.
What Is ACR?
ACR stands for:
Albumin-to-Creatinine Ratio
The laboratory measures:
- albumin in your urine;
- creatinine in your urine;
and compares the two.
Why use a ratio?
The amount of water in your urine changes throughout the day. Sometimes urine is concentrated and sometimes it is dilute.
Using the ratio helps make the albumin result more useful despite these changes.
You may see the test written on a report as:
- ACR;
- urine ACR;
- UACR;
- albumin-creatinine ratio.
They refer to the same basic type of test.
How Is the Test Done?
Usually, you simply provide a urine sample in a clean specimen container.
A first-morning urine sample may sometimes be preferred.
However, a urine sample collected at another time can also be used in many situations.
For routine ACR testing, you usually do not need to collect your urine for 24 hours.
Follow any specific instructions given by your doctor or laboratory.
Do I Need to Fast?
Usually, you do not need to fast just for a urine ACR test.
However, if you are having blood tests or other investigations at the same time, those tests may have their own preparation instructions.
Follow the instructions given for your particular tests.
Why Would My Doctor Check Urine Albumin?
Doctors use urine albumin testing to look for signs of kidney damage.
It can be particularly useful in people who have a higher risk of kidney disease.
This includes many people with:
- diabetes;
- high blood pressure;
- known kidney disease.
The test may also be repeated in people who already have increased urine albumin to see whether it is changing over time.
What Does My ACR Result Mean?
Your report may give the result in mg/g or mg/mmol.
A simple way of understanding the result is:
| ACR result | General meaning |
|---|---|
| Less than 30 mg/g or less than 3 mg/mmol | Normal to mildly increased |
| 30–300 mg/g or 3–30 mg/mmol | Moderately increased |
| More than 300 mg/g or more than 30 mg/mmol | Severely increased |
These ranges help describe how much albumin is present in the urine.
They do not, by themselves, tell you why the albumin is present or whether you definitely have chronic kidney disease.
Your doctor will interpret the result together with your other kidney tests and medical history.
Where Does “Microalbuminuria” Fit?
The older term microalbuminuria generally refers to an ACR in the moderately increased range:
30–300 mg/g, or approximately 3–30 mg/mmol.
You may still see this term on laboratory requests, reports or older medical information.
So a result described as “microalbuminuria” usually means that the amount of albumin in the urine is increased, but not in the highest range.
Does a High ACR Mean I Have Kidney Disease?
Not always.
A high ACR can be a sign of kidney damage, but doctors do not usually diagnose chronic kidney disease from one unexpected abnormal result alone.
The test may need to be repeated.
Your doctor will also consider other information such as:
- your eGFR;
- your creatinine;
- whether you have diabetes or high blood pressure;
- previous results;
- your overall health.
An abnormal result that continues to be present over time is more important than a single isolated result.
Can ACR Be High Temporarily?
Yes.
Urine albumin can sometimes increase temporarily.
This may happen around situations such as:
- strenuous exercise;
- fever or another acute illness;
- urinary infection;
- significant dehydration.
This is one reason why an unexpected abnormal result may sometimes be repeated.
Do not assume that a high result is harmless, however. Let your doctor decide whether and when the test should be repeated.
Can My ACR Be High Even If My eGFR Is Normal?
Yes.
ACR and eGFR tell us different things.
eGFR
This estimates how well your kidneys are filtering your blood.
ACR
This checks whether an increased amount of albumin is leaking into your urine.
This means a person can have increased urine albumin even while the eGFR is still relatively well preserved.
Doctors may therefore use both tests when assessing kidney health.
For more information, read eGFR Explained.
Two Different Clues About Your Kidneys
Why Is This Test Important in Diabetes?
Diabetes can gradually damage the kidneys.
An increase in urine albumin can sometimes be an early sign that the kidneys are being affected.
This is why people with diabetes may be asked to have both:
- a blood test to check kidney function;
- a urine test for albumin.
Having a normal blood kidney result does not always mean that urine albumin testing is unnecessary.
What About High Blood Pressure?
High blood pressure can also affect the kidneys over time.
For some people with high blood pressure, urine albumin testing can provide additional information about kidney health.
A high result does not tell you the cause by itself. It still needs to be considered together with your blood pressure, blood tests and medical history.
Is ACR the Same as a Routine Urine Test?
No.
A routine urine test can look for several things in urine, including protein, blood, glucose and signs of infection.
ACR is a more specific test that measures albumin and compares it with urine creatinine.
The two tests therefore provide different information.
A person may sometimes have an increased ACR even when a routine urine test has not shown obvious protein.
A separate article explaining the Urine Full Report (UFR) / urinalysis covers routine urine testing.
Why Might My Doctor Repeat the Test?
Urine albumin can vary.
If your first result is high, repeating the test can help show whether the increase is temporary or continues to be present.
Repeat testing can also be useful for people who are already known to have albuminuria or kidney disease.
The important point is:
Already Have Your Report?
If you already have a urine albumin or ACR result, you can use our report-reader tools to understand the values shown on your report.
When Should I Speak to a Doctor?
Arrange medical review if you have been told that albumin or protein is repeatedly present in your urine.
This is particularly important if you also have:
- diabetes;
- high blood pressure;
- abnormal creatinine or eGFR;
- known kidney disease.
An abnormal ACR result does not tell you the cause by itself. Further assessment may sometimes be needed.
Remember
One abnormal ACR does not automatically mean chronic kidney disease.
A normal eGFR does not always rule out early kidney damage.
Your results should be interpreted together.
Related kidney health topics
Key Points
- Albumin is a protein normally found in your blood.
- Healthy kidneys allow very little albumin to enter the urine.
- Increased urine albumin is called albuminuria.
- ACR compares urine albumin with urine creatinine.
- “Microalbumin” and “microalbuminuria” are older terms that are still commonly used.
- An ACR above 30 mg/g or 3 mg/mmol is increased.
- One abnormal result does not automatically mean chronic kidney disease.
- ACR can sometimes rise temporarily.
- eGFR and ACR provide different information about kidney health.
- Diabetes and high blood pressure are common reasons for checking urine albumin.
- Your doctor may repeat an abnormal test before making conclusions.