What is an Abnormal UACR?
An abnormal urine albumin-to-creatinine ratio (UACR) is defined as ≥30 mg/g creatinine, with values of 30-299 mg/g indicating moderately increased albuminuria and values ≥300 mg/g indicating severely increased albuminuria. 1
Defining Normal vs. Abnormal Values
- Normal UACR is <30 mg/g creatinine 1
- Moderately increased albuminuria (formerly "microalbuminuria"): 30-299 mg/g creatinine 1, 2
- Severely increased albuminuria (formerly "macroalbuminuria"): ≥300 mg/g creatinine 1, 2
Critical Confirmation Requirements
Due to high biological variability (>20%), you must confirm abnormal values with 2 out of 3 specimens collected within a 3-6 month period before diagnosing persistent albuminuria. 1, 2 A single elevated value is insufficient for diagnosis.
Factors That Can Falsely Elevate UACR
Before confirming chronic kidney disease, exclude these transient causes that can independently elevate UACR: 1
- Exercise within 24 hours
- Active infection or fever
- Congestive heart failure
- Marked hyperglycemia
- Menstruation
- Marked hypertension
Understanding UACR as a Continuous Variable
**UACR is a continuous measurement where risk increases progressively even within the "normal" range (<30 mg/g).** 1, 2 Recent research suggests that values >10 mg/g in patients with type 2 diabetes may predict future chronic kidney disease progression, though this remains below the clinical threshold for intervention. 3
Clinical Significance by Population
Type 1 Diabetes
- Abnormal UACR typically develops after 10+ years of diabetes duration 2, 4
- Usually accompanied by diabetic retinopathy 4
- Rare to develop kidney disease without retinopathy 4
Type 2 Diabetes
- Abnormal UACR may be present at diagnosis due to uncertain disease onset 2, 4
- Can occur with or without retinopathy 4
- More heterogeneous presentation patterns 4
Optimal Collection Technique
- Use first morning void specimens to minimize variability (coefficient of variation 31%) 2
- Avoid food intake for 2 hours prior to collection 2
- Collect at the same time of day for consistency 2
- Avoid collection within 24 hours of exercise 2
When Abnormal UACR Requires Action
For UACR 30-299 mg/g: Initiate ACE inhibitor or ARB therapy regardless of baseline blood pressure, target BP <130/80 mmHg, and monitor every 6-12 months depending on eGFR. 2
For UACR ≥300 mg/g: Immediate intervention with ACE inhibitor or ARB, more frequent monitoring (every 3-6 months), and consider nephrology referral for persistent elevation or declining eGFR. 2
Common Pitfall to Avoid
Do not rely on albumin measurement alone without creatinine correction, as this is susceptible to false-negative and false-positive results due to variations in urine concentration from hydration status. 1 Always use the albumin-to-creatinine ratio for accurate assessment.