Diurnal Variations of Serum and Urine Creatine and Creatinine

Abstract

Diurnal variations in serum and urine creatine and creatinine were observed in normal healthy subjects and in totally paralyzed patients. Serum concentrations and urinary excretion rates were at their peak during the daytime. In fasting subjects there were no variations. The influence of normal meals on creatinine production is stressed. The diurnal food-dependent variations should be taken into acount when serum creatinine values are compared from day to day and when 24-hour creatinine clearances are calculated.