Why is Urine Albumin-Creatinine Ratio (UACR) High? Causes, Symptoms, and What to Do

A high urine albumin-creatinine ratio (UACR, often printed as "alb/creat ratio" or "microalbumin/creatinine ratio") means more albumin, a blood protein, is passing into your urine than healthy kidneys normally allow. A result of 30 mg/g (3 mg/mmol) or more can be an early sign of kidney damage, most often linked to diabetes or high blood pressure, but a single raised result can also come from temporary causes such as intense exercise, fever or a urinary tract infection. That is why a high result is usually repeated before anyone calls it kidney disease. A raised UACR on its own causes no symptoms.

What the test measures

Healthy kidneys keep albumin in the blood and let through at most a trace. The UACR compares the albumin in a single urine sample with the creatinine (a waste product) in the same sample. Comparing the two lets one spot sample estimate how much albumin passes into the urine over 24 hours, without a full 24-hour collection.

UACR is usually ordered together with a blood test for eGFR (estimated glomerular filtration rate), which shows how well the kidneys filter. The two answer different questions: eGFR measures filtering, UACR measures leakage. Albumin in the urine can signal kidney disease even when eGFR is normal (60 or above).

UACR ranges

Some laboratories (for example in the US) report mg/g; others (for example NHS laboratories in the UK) report mg/mmol. The two cut-offs are rounded equivalents, not an exact conversion. Ranges and reporting styles vary slightly between laboratories and methods, so compare your number with the range printed on your own report.

The moderately increased band was traditionally called "microalbuminuria", which is why some reports still say "microalbumin". The higher the number, the higher the risk of kidney failure, heart attack, stroke and heart failure.

Why UACR can be high

Common, long-term causes

• Diabetes. Years of high blood sugar damage the tiny filters (glomeruli) in the kidneys, so they start to leak albumin. This is why people with diabetes are checked every year.
• High blood pressure. Raised pressure strains and damages the same filters over time. Diabetes and high blood pressure are the two main risk factors.
• Chronic kidney disease from other causes. Any disease that damages the filters, including inflammation of the filters (glomerulonephritis), lets more albumin through.
• Heart disease or heart failure, obesity, smoking, older age and a family history of kidney disease are risk factors for which regular testing is advised.

Temporary causes (a reason to repeat the test)

• Intense exercise in the 24 hours before the sample.
• Fever or infection, including a urinary tract infection.
• Menstrual blood or other bleeding into the urine.
• A sudden large rise in blood pressure or blood sugar, or a flare-up of heart failure.
• Dehydration.
• Certain medicines; ask your provider whether any of yours could affect the result.
• Other inflammatory conditions, such as gum infection (periodontitis) or hepatitis, which can also raise urine albumin.
• Orthostatic proteinuria, a harmless pattern mostly seen in children and teenagers, where protein appears in urine only while upright.

Less common causes

Specific kidney diseases (such as lupus nephritis, membranous nephropathy, minimal change disease or amyloidosis), preeclampsia in pregnancy, and blood disorders such as multiple myeloma can also put protein into the urine. These are found through further testing, not from the UACR alone.

Symptoms of a high albumin-creatinine ratio

A raised UACR itself does not cause symptoms. Early kidney disease usually has none either, which is exactly why the test is used for screening. When symptoms do appear, they belong to larger protein losses or more advanced disease, and may include:

• frothy or foamy urine;
• puffiness around the eyes on waking;
• swelling of the legs, ankles or abdomen.

Tiredness or poor concentration are not specific to a high UACR and should not be read as proof of kidney damage.

What a low UACR means

There is no "too low" result. A low or undetectable UACR, or a low microalbumin, is the normal and desired finding: for this test, lower is better. Muscle mass, diet and age can affect the result, so a low result is still read alongside your eGFR and risk factors.

What usually happens next

1. Repeat the test. A first result of 30 mg/g or more is usually repeated within 3 to 6 months, ideally on an early-morning sample. If two out of three samples are raised, kidney disease may be present. Decisions are rarely based on one sample.
2. Check eGFR. A blood creatinine test with eGFR shows filtering function. Albuminuria that stays raised for 3 months or more, even with a normal eGFR, may mean chronic kidney disease.
3. Look for the cause. Depending on your history, a clinician may order a urinalysis with microscopy (looking for blood or infection), blood glucose, a blood pressure check, a complete blood count, electrolytes and, in some cases, a kidney ultrasound. If protein stays high without a clear reason, more specialised blood tests and, occasionally, a kidney biopsy may follow.
4. Follow-up testing. How often UACR is repeated, from once a year to four or more times a year, depends on your condition, the first UACR and your eGFR.

The interpretation depends on the trend over repeat samples, your eGFR, and whether anything temporary was present on the test day.

Frequently asked questions

What does a high albumin-creatinine ratio mean?

It means albumin is leaking into your urine. If it is confirmed on repeat testing, it is a sign of kidney damage, most often from diabetes or high blood pressure, and it signals higher risk to both kidneys and heart. A single high result may also be temporary.

What are the symptoms of a high albumin-creatinine ratio?

Usually none. Symptoms such as foamy urine or swelling appear only with larger protein losses or more advanced kidney disease.

What does a UACR of 50 mg/g mean?

It falls in the moderately increased range (30 to 300 mg/g). It is a reason to repeat the test within a few months and check your eGFR. If it is confirmed over 3 months or more, it may indicate chronic kidney disease.

Can a urine ACR be raised for a harmless reason?

Yes. Intense exercise, fever, a urinary tract infection, menstrual blood, dehydration or a sudden rise in blood sugar or blood pressure can raise it temporarily. Your provider may suggest repeating the test when these are no longer present.

Is a low microalbumin or low albumin-creatinine ratio bad?

No. A low result is normal; lower is better for this test.

Do I need to fast for a UACR test?

The usual instructions do not include fasting. You may be asked to avoid intense exercise for 24 hours beforehand, to drink normally, and sometimes to avoid meat the day before. An early-morning sample is preferred. Tell the person collecting the sample if you are menstruating.

How often should UACR be checked?

People with diabetes are usually tested every year. People with high blood pressure, heart disease, a family history of kidney disease or other risk factors should ask their provider how often to test.

When to see a doctor

If your UACR is 30 mg/g (3 mg/mmol) or higher, it is worth discussing with your doctor soon, mainly to arrange a repeat test and an eGFR. There is no need for alarm about a single value, especially if you exercised hard, had a fever or infection, or were menstruating. If you notice new swelling of the legs or face, or foamy urine that persists, mention it at that visit. If you have diabetes or high blood pressure and have not had a UACR in the past year, ask about it.

Sources

1. Microalbumin Creatinine Ratio — MedlinePlus, U.S. National Library of Medicine
2. Urine albumin-creatinine ratio (uACR) — National Kidney Foundation
3. Urine test: uACR (urine albumin-to-creatinine ratio) — American Kidney Fund
4. Chronic Kidney Disease Tests & Diagnosis — NIDDK
5. Proteinuria — Merck Manual Professional Version
6. Albumin (urine) — University Hospitals Sussex NHS Trust Pathology

Decisions about your health should always be made in consultation with your healthcare provider.