Albumin is a large protein molecule that, under healthy conditions, is almost completely retained by the kidney's filtering units (glomeruli). The urine albumin test, also known as a microalbumin test when measuring very small amounts, detects even tiny increases of albumin in the urine—amounts too low to be found with a standard urine dipstick.
This test is commonly used to screen for early kidney damage (nephropathy) in people with diabetes or high blood pressure, because albumin leakage into the urine can be one of the earliest signs of glomerular injury. Regular monitoring helps guide treatment and slow progression of kidney disease.
Measuring urine albumin is important because early kidney damage often has no symptoms. Detecting and managing it can prevent more serious kidney problems. The test is usually performed on a random (spot) urine sample, and results may be reported as albumin concentration or as an albumin-to-creatinine ratio to account for urine dilution.