What is the urinary albumin‑to‑creatinine ratio, its normal and abnormal thresholds, recommended screening frequency, and recommended management for elevated results?

Urinary Albumin-to-Creatinine Ratio (UACR): Definition, Thresholds, Screening, and Management

What UACR Measures

UACR is a spot urine test that quantifies albumin excretion normalized to creatinine concentration, serving as the gold standard for detecting and monitoring kidney damage in diabetes and chronic kidney disease. 1

• UACR is measured in milligrams of albumin per gram of creatinine (mg/g) from a random spot urine sample, preferably first morning void. 1
• The test specifically measures albumin (not total protein), making it more sensitive for early glomerular damage than total protein measurements. 2
• Spot UACR eliminates the need for cumbersome 24-hour urine collections, which add little predictive value and are prone to collection errors. 1

Normal and Abnormal Thresholds

The American Diabetes Association defines three categories:

• Normal (A1): <30 mg/g creatinine 1
• Moderately increased albuminuria (A2): 30–299 mg/g creatinine (formerly called "microalbuminuria") 1
• Severely increased albuminuria (A3): ≥300 mg/g creatinine (formerly called "macroalbuminuria") 1

Important nuance: UACR is a continuous risk marker—even values within the "normal" range (<30 mg/g) correlate with cardiovascular and renal outcomes, with risk escalating progressively as values rise. 1, 3 Recent research suggests UACR values >10 mg/g in men or >8 mg/g in women may predict CKD progression in type 2 diabetes, though these lower thresholds are not yet incorporated into clinical guidelines. 4

Screening Frequency

For type 1 diabetes: Begin screening 5 years after diagnosis, then annually. 1, 3

For type 2 diabetes: Screen at the time of diagnosis (because disease onset is uncertain), then annually. 1, 3

Intensified monitoring based on results:

UACR Category	eGFR (mL/min/1.73 m²)	Monitoring Frequency
30–299 mg/g	≥60	Annually [3]
30–299 mg/g	45–59	Every 6 months [3]
30–299 mg/g	30–44	Every 3–4 months [3]
≥300 mg/g	>60	Every 6 months [3]
≥300 mg/g	30–60	Every 3 months [3]
Any UACR	<30	Immediate nephrology referral [3]

Confirmation Requirements Before Diagnosis

Due to high biological variability (coefficient of variation ~48%), obtain 2 out of 3 elevated samples (≥30 mg/g) over a 3–6 month period before confirming persistent albuminuria. 1, 5

Exclude transient causes before confirming chronic elevation:

• Exercise within 24 hours 1, 3
• Active urinary tract infection or fever 1, 3
• Menstruation 1, 3
• Congestive heart failure exacerbation 1, 3
• Marked hyperglycemia 1, 3
• Uncontrolled hypertension 1, 3

Management of Elevated UACR

For UACR 30–299 mg/g (Moderately Increased Albuminuria)

Initiate an ACE inhibitor or ARB immediately, regardless of baseline blood pressure, because these agents provide kidney-protective effects beyond simple blood pressure lowering. 1, 3

• Target blood pressure <130/80 mmHg. 1, 3
• Optimize glycemic control as the primary prevention strategy for diabetic kidney disease progression. 1, 3
• Restrict dietary protein to 0.8 g/kg/day (the recommended daily allowance). 1, 3
• Lipid management: LDL <100 mg/dL if diabetic, <120 mg/dL otherwise; saturated fat <7% of total calories. 3
• Therapeutic goal: Reduce UACR by at least 30–50%, ideally achieving <30 mg/g. 3

For UACR ≥300 mg/g (Severely Increased Albuminuria)

All interventions above apply, plus:

• ACE inhibitor or ARB therapy is strongly recommended even in the absence of hypertension. 3
• Monitor every 3–6 months depending on eGFR. 3
• Consider nephrology referral for persistent UACR ≥300 mg/g despite optimal therapy. 3

Immediate Nephrology Referral Indications

• eGFR <30 mL/min/1.73 m² 3
• Rapid decline in eGFR or rapidly increasing albuminuria 1
• Active urinary sediment (red/white blood cells, cellular casts) 1
• Nephrotic syndrome 1
• Absence of diabetic retinopathy in type 1 diabetes (suggests alternative kidney disease) 1
• Refractory hypertension requiring ≥4 antihypertensive agents 3
• Inadequate response to optimal ACE inhibitor/ARB therapy 3

Critical Pitfalls to Avoid

Do not measure albumin alone without creatinine correction—variations in urine concentration from hydration status produce false results. 1

Do not rely on a single UACR measurement—day-to-day variability is substantial (a repeat sample can be 0.26 to 3.78 times the initial value). 5, 6 For patients with normoalbuminuria, a change >467% is required to indicate true change; for microalbuminuria, >170%; for macroalbuminuria, >83%. 6

Do not use 24-hour urine collections for routine screening—they are burdensome, error-prone, and add no predictive advantage over spot UACR. 1

First morning void samples are preferred to minimize variability and exclude orthostatic proteinuria, especially in younger patients. 3, 7

ACE inhibitors and ARBs are contraindicated in pregnancy—ensure reliable contraception in women of childbearing age before initiating therapy. 3