VARIABILITY OF CREATININE EXCRETION IN NORMAL SUBJECTS, MENTAL PATIENTS AND PREGNANT WOMEN

The daily urinary excretion of creatinine has been examined in normal subjects and in patients with mental disorders over periods of several weeks. The excretion was reasonably constant in some individuals but showed considerable variation in others. The meat content of the diet influenced the amount of creatinine excreted, but variability in excretion was also seen in a group of nine subjects on a constant protein and fluid intake. In some individuals there was a strong statistical correlation between the volume of the urine sample and the creatinine content, and study of total body potassium and creatinine excretion in two patients showed a correlation between these two factors. A fall in the amounts of creatine and creatine+creatinine excreted in pre-eclamptic toxaemia of pregnancy was found as compared with normal pregnancy. It is concluded that the use of creatinine excretion as a measure of the completeness of a 24-hour urine sample is unreliable in some individuals. © 1969.