[Urea and creatinine levels and clearances: observations in 25 healthy subjects for one year (author's transl)].

The seasonal, intra- und interindividual variation of the creatinine and urea concentrations in serum and urine and the clearances of these compounds were examined monthly for one year in 25 healthy volunteers. In contrast to the other parameters (serum urea, clearance and excretion of creatinine and urea), the variations in serum-creatinine concentration were small and statistically unsignificant. The variations of the urinary excretion and the clearance of creatinine and urea is due to seasonal variations in the output of the kidney.