UACR

Urine Albumin-to-Creatinine Ratio

Urinalysis

What is Urine Albumin-to-Creatinine Ratio?

The urine albumin-to-creatinine ratio (UACR) is a convenient and standardized method for quantifying urinary albumin excretion from a spot (random) urine sample, eliminating the need for a timed 24-hour urine collection. Albumin is a large protein that is normally retained by the glomerular filtration barrier. When the kidneys are damaged, this barrier becomes more permeable, allowing albumin to leak into the urine—a condition known as albuminuria. By dividing the urine albumin concentration by the urine creatinine concentration, the UACR corrects for variations in urine dilution, providing a reliable estimate of daily albumin excretion.

UACR is the recommended test for detecting and monitoring albuminuria, which is a hallmark of diabetic kidney disease and a key marker in the staging of chronic kidney disease (CKD). Current KDIGO guidelines classify albuminuria into three categories: normal to mildly increased (<30 mg/g), moderately increased (30–300 mg/g, formerly called "microalbuminuria"), and severely increased (>300 mg/g, formerly called "macroalbuminuria"). UACR is also an independent cardiovascular risk factor—elevated albuminuria predicts heart attack, stroke, and heart failure even in the absence of overt kidney disease.

Why It Matters

UACR is one of the earliest detectable markers of kidney damage, often appearing years before eGFR begins to decline. In diabetes, persistent moderately increased albuminuria is the first clinical sign of diabetic nephropathy and identifies patients who benefit most from intensified treatment with RAAS inhibitors (ACE inhibitors or ARBs), SGLT2 inhibitors, and tight glycemic control. UACR is also a powerful cardiovascular risk predictor—each doubling of UACR is associated with a 29% increase in cardiovascular mortality. Monitoring UACR allows clinicians to detect kidney damage early, guide treatment decisions, and track response to therapy.

Normal Reference Ranges

Group	Range	Unit
Normal	<30	mg/g
Moderately increased (microalbuminuria)	30–300	mg/g
Severely increased (macroalbuminuria)	>300	mg/g

Reference ranges may vary by laboratory. Always compare results to the ranges provided by your testing facility.

What High UACR Levels Mean

Common Causes

Diabetic nephropathy (most common cause globally)
Hypertensive nephrosclerosis
Glomerulonephritis (IgA nephropathy, membranous, focal segmental glomerulosclerosis)
Lupus nephritis
Preeclampsia
Heart failure
Urinary tract infection (transient elevation)
Intense exercise or fever (transient elevation)
Obesity

Possible Symptoms

Usually asymptomatic in early stages
Foamy or frothy urine (with significant proteinuria)
Swelling in feet, ankles, or around eyes (nephrotic range)
Fatigue
Elevated blood pressure

What to do: Elevated UACR should be confirmed with at least two of three specimens over 3–6 months, as transient causes (exercise, UTI, fever) can produce false positives. If persistently elevated, evaluate for underlying causes: check blood glucose and HbA1c (diabetes), blood pressure, serum creatinine and eGFR, serum albumin, and urinalysis for active sediment. Treatment focuses on the underlying cause and renoprotective measures: ACE inhibitors or ARBs reduce albuminuria and slow CKD progression, SGLT2 inhibitors provide additional renoprotection, and blood pressure and glycemic targets should be optimized.

What Low UACR Levels Mean

Common Causes

Normal kidney function
Effective treatment reducing albuminuria

Possible Symptoms

No symptoms associated with low UACR

What to do: A UACR below 30 mg/g is normal and indicates intact glomerular filtration barrier function. Continue regular screening if risk factors are present (diabetes, hypertension). A reduction in UACR with treatment correlates with improved renal and cardiovascular outcomes.

When Is UACR Testing Recommended?

Annual screening in all patients with diabetes (type 1 after 5 years, type 2 at diagnosis)
Annual screening in patients with hypertension
Evaluation and staging of chronic kidney disease
Monitoring response to renoprotective therapy (ACE inhibitor, ARB, SGLT2 inhibitor)
Cardiovascular risk assessment
Preeclampsia evaluation in pregnancy

Frequently Asked Questions

UACR from a spot urine sample is more convenient and is now the recommended test for detecting albuminuria. It correlates well with 24-hour urine albumin excretion. A 24-hour collection may still be used when precise quantification is needed or when non-albumin proteinuria is suspected, as UACR measures only albumin, not total protein.

Yes. Vigorous exercise within 24 hours before testing can transiently increase urinary albumin excretion. Other causes of transient elevation include fever, urinary tract infection, uncontrolled hypertension, heart failure exacerbation, and acute illness. For this reason, guidelines recommend confirming elevated UACR with at least two positive results over 3–6 months before diagnosing persistent albuminuria.

A first-morning urine sample is preferred because it reduces variability from activity, posture, and hydration. However, a random spot urine UACR is acceptable and is the standard for clinical practice when a first-morning sample is not feasible.

Related Biomarkers

CrCreatinine eGFREstimated Glomerular Filtration Rate

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Medical Disclaimer: This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Reference ranges may vary between laboratories. Always consult your healthcare provider for interpretation of your specific test results.