Microalbuminuria: what a raised urine ACR means

Albumin is a protein found in the blood. Healthy kidneys keep almost all of it in the circulation. When the filters begin to leak, a little albumin escapes into the urine. If the amount is too small for a standard urine dipstick, it is called microalbuminuria and is measured by a laboratory test, the urine albumin to creatinine ratio, or ACR.

Lab Tests Online UK explains that the test compares the amount of albumin with creatinine, so that the result is not thrown off by how much water you have drunk. It adds that ACR in a random sample has been shown to be just as good as measuring albumin in a 24-hour collection, and is more convenient.

The word microalbuminuria is still widely used, although laboratories and the NHS tend to talk about the ACR result itself, described as normal, moderately increased or very high.

The NHS says that identifying kidney disease early in people with diabetes allows appropriate treatment to be given and its effects monitored. Lab Tests Online UK states that the ACR is used to screen for and detect early kidney damage, particularly in people with diabetes or high blood pressure, and that it is usually measured annually after a diagnosis of diabetes or hypertension. It does not require special preparation.

NHS pages on chronic kidney disease (CKD) add that there are usually no symptoms of kidney disease in the early stages and that it may only be diagnosed if a blood or urine test for another reason shows a possible problem. People at higher risk, for example with diabetes or high blood pressure, may be advised to have regular tests so that CKD is found early.

The NHS says that a slightly raised ACR may mean early-stage kidney disease, that a very high level indicates more severe disease, and that a very low value probably means your kidneys are working normally. Lab Tests Online UK similarly says a moderately increased ACR indicates an early phase of developing kidney disease, and that very low values generally indicate normal kidney function if other tests such as the glomerular filtration rate are also normal.

Because several harmless factors can temporarily raise the ACR, a single abnormal result is usually repeated before a diagnosis is made. Lab Tests Online UK lists fever, urinary tract infection, immune disorders, dehydration, certain drugs, conditions that cause blood in the urine and vigorous exercise. Your doctor will also look at your kidney function blood test (eGFR) and blood pressure to build a complete picture.

A raised ACR that persists, together with eGFR, is used to help stage chronic kidney disease. The NHS notes that results of blood and urine tests are used to tell the stage of CKD, with a higher number indicating more serious disease. Remember that most people with CKD can control it with medicine and regular check-ups.

The NHS says that if diabetes is well managed it is easier to control or prevent complications such as high blood pressure, which can sometimes lead to kidney disease. Lab Tests Online UK adds that good control of diabetes and other conditions such as high blood pressure can slow or prevent progression of kidney disease.

For CKD more generally, the NHS lists lifestyle changes, medicine to control associated problems such as high blood pressure and high cholesterol, and medicine that can help the kidneys keep working for longer, with regular check-ups. It also says that CKD only progresses to kidney failure in around 2 in 100 people with the condition. Medicines should not be started or stopped on the basis of an ACR alone: speak to your GP or diabetes team.

Lab Tests Online UK notes that recent studies show that in people with type 2 diabetes an abnormal ACR indicates an increased risk of developing heart and blood vessel disease. The NHS CKD page also says that even mild CKD increases the risk of cardiovascular disease, though healthy lifestyle changes and medicine can help reduce it. A raised ACR is therefore not just a kidney marker; it is a prompt to look at overall cardiovascular risk.

In the NHS, ACR is arranged by GP surgeries and diabetes clinics as part of annual reviews, and results are usually discussed at the next appointment or via the NHS App. Private health checks sometimes include a urine ACR as well. If a private ACR is raised, the most useful step is to share it with your GP so that it can be repeated and interpreted with your kidney function and blood pressure.