Diabetic nephropathy, or diabetic kidney disease, affects 20 to 30 percent of patients with diabetes. It is a common cause of kidney failure. Diabetic nephropathy presents in its earliest stage with low levels of albumin (microalbuminuria) in the urine. The most practical method of screening for microalbuminuria is to assess the albumin-to-creatinine ratio with a spot urine test. Results of two of three tests for microalbuminuria should be more than 30 mg per day or 20 mcg per minute in a three- to six-month period to diagnose a patient with diabetic nephropathy. Slowing the progression of diabetic nephropathy can be achieved by optimizing blood pressure (130/80 mm Hg or less) and glycemic control, and by prescribing an angiotensin-converting enzyme inhibitor or angiotensin receptor blocker. Patients with diabetes and isolated microalbuminuria or hypertension benefit from angiotensin-converting enzyme inhibitors or angiotensin receptor blockers. In the event that these medications cannot be prescribed, a nondihydropyridine calcium channel blocker may be considered. Serum creatinine and potassium levels should be monitored carefully for patients receiving angiotensin-converting enzyme inhibitors or angiotensin receptor blockers. These medications should be stopped if hyperkalemia is pronounced.