Urine ACR test: checking for albumin in your urine

What the test measures

Albumin is the main protein in your blood. Healthy kidney filters keep almost all of it in the blood, so only a very small amount reaches the urine. When the filters are damaged, for example by long-standing diabetes or high blood pressure, more albumin leaks through. Albumin in the urine is called albuminuria.

The amount of albumin in a single urine sample depends on how concentrated the urine is. To correct for this, the lab also measures creatinine in the same urine sample and reports albumin as a ratio to creatinine. That ratio is the ACR. It gives a reliable picture from one spot sample, without collecting urine over 24 hours.

You may see the older term "microalbuminuria" on some forms. It describes what is now called moderately increased albuminuria (category A2 below).

Why it is ordered

KDIGO 2024 guidance places urine albumin alongside eGFR in the evaluation of chronic kidney disease (CKD). Both are needed: someone can have a normal eGFR and still have kidney damage that shows up only as albumin in the urine. ACR is commonly requested:

• as a yearly check for people with diabetes (see kidney tests for diabetes)
• for people with high blood pressure, heart disease or a family history of kidney disease
• when a urine dipstick shows protein, to measure it accurately
• when a creatinine or eGFR result is abnormal
• to follow known CKD and see how it responds to care

Raised albumin in the urine is also linked with a higher risk of heart and blood vessel disease, which is another reason clinicians track it.

How the sample is taken and how to prepare

You give a small urine sample in a clean container from the lab. No blood is needed for the ACR itself.

• An early morning sample is often preferred. The first urine you pass after waking gives the most consistent result. If the lab asks for one, pass that urine into the container at home and bring it in the same morning, kept cool.
• Avoid heavy exercise in the 24 hours before the test, as it can raise albumin in the urine for a short time.
• Postpone the test during a period if possible, or tell the lab, because blood in the sample can affect the result.
• Tell the clinician if you are unwell with fever or a urine infection. It is usually better to test once you have recovered.

A random sample taken at the clinic is acceptable for a first check. If it is raised, a repeat early morning sample is usually requested.

How results are reported

Labs report ACR in one of two units. Kenyan labs use both, depending on their equipment:

• mg/mmol: milligrams of albumin per millimole of creatinine
• mg/g: milligrams of albumin per gram of creatinine

A result in mg/g is roughly ten times the same result in mg/mmol, so check the unit before comparing reports. KDIGO groups ACR into three categories:

The A category is combined with the eGFR G category to describe CKD and to guide how often tests are repeated. For example, a person might be described as "G2 A2". Our page on CKD stages explains the combined grid.

What can affect the result

ACR can rise for a short time for reasons that have nothing to do with lasting kidney damage:

• vigorous exercise in the previous day
• a urine infection, or any illness with fever
• menstrual blood or vaginal discharge in the sample
• very high blood sugar or very high blood pressure at the time of the test
• heart failure that is not well controlled
• standing for long periods, in some young people (the early morning sample helps avoid this)

Because of this natural variation, a raised result is usually confirmed with at least one repeat sample, often an early morning one, before any conclusion is drawn. For CKD, the increase must also last more than 3 months.

What ACR cannot tell you on its own

ACR shows that albumin is leaking. It does not say why. Diabetes, high blood pressure, inflammation of the kidney filters and other conditions can all cause it, and finding the cause may need other tests. ACR also does not measure filtration: that is the job of the eGFR. The two results are read together.

Very high levels of protein, well into A3, can be part of a condition in which the body loses so much protein that swelling develops. Some clinicians also use a urine protein to creatinine ratio (PCR), which measures all proteins, not only albumin. Your clinician will choose which test fits your situation.

Related tests

• eGFR: the filtration estimate that ACR is paired with.
• Urinalysis: a general urine screen that includes a dipstick for protein.
• Creatinine test: the blood test used to calculate eGFR.
• Protein in urine: what it can mean and what to check.

When to discuss your result with a clinician

See a doctor or clinical officer if your ACR is in category A2 or A3, if it has risen compared with an earlier result, or if you have diabetes or high blood pressure and have not had an ACR test in the past year. An ACR in A3 usually needs prompt review, and a clinician may discuss referral to a kidney specialist. Bring your earlier urine and blood results with you, including any from a different lab.

Common questions

Is ACR the same as the protein on a urine dipstick?

No. A standard dipstick picks up protein only when there is quite a lot of it. ACR is a laboratory test that measures albumin precisely, so it finds smaller amounts much earlier. A negative dipstick does not rule out a raised ACR.

How often should ACR be checked?

This depends on your health. People with diabetes are usually advised to have ACR checked at least once a year, and people with high blood pressure or known kidney disease are checked regularly. Your clinician will set the interval based on your results.

Can a raised ACR go back down?

Yes, it can. ACR can fall after a urine infection clears, or when blood sugar and blood pressure are better controlled. Some treatments a clinician may consider are aimed partly at reducing albumin in the urine. Repeat tests show the direction of change.

This page explains what a test or condition involves. It is not a diagnosis and does not replace advice from a doctor who knows your history. Your results should be interpreted together with your symptoms, other tests and a clinical assessment. Medical disclaimer.