The urine albumin-to-creatinine ratio (ACR) is a urine test that measures albumin relative to creatinine. Increased urine albumin may be an early sign of kidney damage, especially in people with diabetes, high blood pressure or other kidney disease risk factors.
Urine ACR and estimated glomerular filtration rate (eGFR) provide complementary information about kidney health. A single abnormal ACR result does not automatically establish chronic kidney disease and may require repeat testing and medical evaluation.
A urine ACR test measures the concentration of albumin and creatinine in a spot urine sample and then calculates the ratio, usually expressed in milligrams of albumin per gram of creatinine (mg/g). This ratio corrects for variations in urine concentration, making it more reliable than a simple urine protein test. According to the National Kidney Foundation, the uACR is the preferred screening tool for detecting albuminuria in people at risk for chronic kidney disease (CKD).
Kidneys filter waste while keeping essential proteins like albumin in the bloodstream. When the glomeruli become damaged, albumin leaks into the urine, a condition called albuminuria or proteinuria. Detecting this leak early can:
For people with diabetes, the Kidney Fund notes that routine uACR screening is essential because diabetic kidney disease often begins with microalbuminuria.
The test requires a clean‑catch midstream urine sample, which can be collected at home or in a clinic. No fasting is needed, but the sample should be taken when the bladder is neither empty nor overly full. The laboratory measures albumin (mg) and creatinine (g) and reports the ratio. Some labs also provide a separate urine albumin test and a urine creatinine test, but the combined ratio is what clinicians use for interpretation.
Results are categorized by the National Kidney Foundation as follows:
Urine ACR results are generally classified into three categories:
| Urine ACR (mg/g) | Category | Meaning |
|---|---|---|
| Below 30 | A1 | Normal to mildly increased |
| 30–300 | A2 | Moderately increased |
| Above 300 | A3 | Severely increased |
Increased urine ACR may indicate kidney damage, but temporary factors such as illness, strenuous exercise or urinary infection can also affect the result.
Results should be interpreted alongside eGFR, medical history and other investigations. Repeat testing may be needed to establish whether albuminuria is persistent.
Traditional urine protein tests measure total protein, which can be influenced by hydration status and muscle mass. The urine ACR test, by normalizing albumin to creatinine, provides a more stable estimate of kidney filtration function. This is why clinicians often prefer the uACR over a generic urine protein test when monitoring diabetic patients or those with hypertension.
For a deeper dive into related kidney tests, see our Kidney Tests Explained: Creatinine, eGFR, Urine ACR & Electrolytes.
When the urine ACR is above 30 mg/g, clinicians consider several possible causes:
Addressing reversible factors—like treating an infection or adjusting medication—can sometimes bring the ACR back into the normal range. Lifestyle changes (tight blood‑pressure control, low‑protein diet, smoking cessation) also help lower albuminuria over time.
eGFR estimates how well the kidneys filter blood, while uACR detects leakage of protein. Both are complementary: a normal eGFR with a high uACR signals early kidney damage, whereas a low eGFR with a normal uACR may indicate non‑proteinuric CKD. Combining these metrics improves risk stratification, as highlighted by the Labcorp ACR test description.
To ensure reliable results, follow these guidelines:
For more on how to prepare for lab tests, read our Protein in Urine Child: When to Seek Kidney Care.
If your first urine ACR result is abnormal, most clinicians will repeat the test after 2–4 weeks to confirm persistence. For patients with known CKD, the test may be ordered every 3–6 months, depending on disease stability and treatment changes. Diabetic patients are often advised to have a urine ACR at least once a year, as recommended by the American Diabetes Association.
Yes, in many cases. Tight glycemic control, blood‑pressure management (especially with ACE inhibitors or ARBs), and lifestyle modifications have been shown to reduce albuminuria. Studies cited by the Siemens Healthineers indicate that up to 30 % of patients can achieve a return to the normal range with appropriate therapy.
Ultimately, early detection through regular urine ACR screening empowers patients and providers to intervene before irreversible kidney damage occurs.
A urine ACR test measures the albumin‑to‑creatinine ratio in a spot urine sample, providing a snapshot of how much albumin is leaking into the urine relative to creatinine.
A high urine ACR (above 30 mg/g) indicates albuminuria, which can be an early sign of kidney damage, especially in diabetes or hypertension.
You provide a clean‑catch midstream urine sample; the lab quantifies albumin and creatinine and calculates the ratio, usually reported in mg/g.
The normal range is less than 30 mg/g; 30–299 mg/g is considered moderately increased (microalbuminuria), and 300 mg/g or higher is severely increased.
Diabetic patients should have a urine ACR test at least once a year, or more frequently if previous results were abnormal or kidney function is declining.
Yes—tight blood‑pressure control, ACE‑inhibitor or ARB therapy, and lifestyle changes can lower albuminuria and sometimes bring the ACR back to normal.
The urine ACR test is an important investigation for identifying albumin leakage and assessing kidney health, especially in people with diabetes, hypertension or other kidney disease risk factors.
Urine ACR and eGFR provide complementary information. Together with medical history and other findings, they help healthcare professionals evaluate possible kidney damage and monitor changes over time.
An elevated urine ACR result does not automatically indicate kidney failure or permanent kidney damage. Confirmation, clinical interpretation and appropriate follow-up are important.
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