The persistent appearance of small amounts of albumin (microalbuminuria) in urine could be the first indicator of a renal dysfunction. For persons with diabetes, a positive result could be the first indicator of a diabetic nephropathy. Without initiation of therapy, the amount of released albumin will increase (macroalbuminuria) and a renal insufficiency will occur. In case of type-2 diabetes, the early diagnosis and therapy of diabetic nephropathy is especially important. In addition to the renal dysfunction, cardiovascular risks could occur. At normal physiological conditions, small amounts of albumin are glomerular filtrated and tubular reabsorbed. The expulsion of 20μg/mL to 200μg/mL is characterized as microalbuminuria. In addition to renal dysfunctions, albuminuria can be caused by physical training, infections of the urinary tract, hypertension, cardiac insufficiency and surgery. If the amount of albumin decreases after disappearance of these factors, the transient albuminuria is without any pathological reason.