Serum amylase in patients with renal insufficiency and renal failure. Results vary with regard to the upper limits of serum amylase seen in patients with renal failure, and very little has been reported with patients with renal insufficiency not yet requiring dialysis. To determine the level of serum amylase elevation in renal insufficiency and renal failure, we determined serum amylase values in 128 subjects with creatinine clearances less than 90 ml/min. Serum amylase remained in the normal range when creatinine clearance was greater than 50 ml/min, and did not become elevated until creatinine clearance was less than 50 ml/min. The highest serum amylase recorded in the absence of acute pancreatitis was 503 IU/L (normal, less than 128 IU/L). Serum lipase and trypsin values paralleled those for serum amylase; values remained normal when creatinine clearance was greater than 50 ml/min, and were normal or elevated when creatinine clearance was less than 50 ml/min. These results indicate that elevations of serum amylase (i.e., amylase greater than 128 but less than 500 IU/L) in asymptomatic patients with impaired renal function are not evident until creatinine clearances fall below 50 ml/min, and probably do not represent acute pancreatitis. 