High serum a1-microglobulin generally indicates damage to the renal proximal tubule. a1-microglobulin, a low molecular protein, is mainly produced by lymphocytes, and is produced most rapidly when the cells are in their most vigorous physiological state. a1-microglobulin passes freely through the glomerular membrane, i.e., most of it is reabsorbed and catabolized by the proximal tubule. Under normal conditions, the amount of a1-microglobulin in the urine is very small, and when the renal tubules are damaged, the urinary a1-microglobulin secretion is increased. It can be seen that a1-microglobulin is an early diagnostic indicator to determine proximal tubular damage and is used as an indicator of renal tubular insufficiency.