Normal Range for Urinary Microalbumin
The normal range for urinary microalbumin is less than 30 mg/g creatinine when measured as an albumin-to-creatinine ratio (ACR) in a spot urine sample. 1
Defining Albuminuria Categories
The American Diabetes Association provides clear thresholds for interpreting urinary albumin excretion 1:
- Normal to mildly increased: <30 mg/g creatinine
- Moderately increased albuminuria (formerly called microalbuminuria): 30-299 mg/g creatinine
- Severely increased albuminuria: ≥300 mg/g creatinine
These cutoffs apply when using the albumin-to-creatinine ratio, which is the preferred method for screening and monitoring 1, 2.
Preferred Testing Method
Use a spot urine albumin-to-creatinine ratio rather than 24-hour urine collections. 2 The ratio corrects for variations in urine concentration due to hydration status, making it far more convenient and reliable than timed collections 2, 3.
- First-morning void specimens are optimal for children and adolescents to avoid orthostatic proteinuria 2, 3
- Random spot urine samples are acceptable in adults 2
Clinical Significance of the Normal Range
Values below 30 mg/g creatinine indicate no microalbuminuria and represent normal kidney function with respect to albumin excretion 2, 3. At any level of estimated GFR, an elevated albumin-to-creatinine ratio above this threshold is associated with increased risk for cardiovascular disease, chronic kidney disease progression, and mortality 3.
Screening Recommendations
Annual screening with albumin-to-creatinine ratio is recommended for adults with diabetes 1, 3. If albuminuria exceeds 30 mg/g creatinine or eGFR falls below 60 mL/min/1.73 m², testing should be repeated every 6 months 1.
Important Caveats
Several factors can falsely elevate the albumin-to-creatinine ratio and should be avoided before testing 3:
- Vigorous exercise within 24 hours of collection
- Acute infection or fever
- Marked hyperglycemia
- Congestive heart failure
- Urinary tract infection
Albumin excretion can vary by 40-50% in individuals, so a single elevated value should be confirmed with repeat testing 1. The American Diabetes Association recommends documenting stage A2 albuminuria (30-299 mg/g) on two of three tests performed within 3-6 months before establishing the diagnosis 1.