Background. Microalbuminuria is defined as excretion of 30–300 mg of albumin per 24 hours (or 20–200 mcg/min or 30–300 mcg/mg creatinine) on 2 of 3 urine collections. The detection of low levels of albumin excretion (microalbuminuria) has been linked to the identification of incipient diabetic kidney disease.ackground. Microalbuminuria is defined as excretion of 30–300 mg of albumin per 24 hours (or 20–200 mcg/min or 30–300 mcg/mg creatinine) on 2 of 3 urine collections. The detection of low levels of albumin excretion (microalbuminuria) has been linked to the identification of incipient diabetic kidney disease.