Variability of daily creatinine excretion in healthy adults.

In order to determine the within-subject variability of creatinine excretion, the 24-h output was measured over 5 consecutive d in 12 subjects. The mean within-subject coefficient of variation was 3.6 per cent. There was much greater variation between subjects. The creatinine excretion in g/d was 30-40 per cent lower in Burmese subjects than in Europeans and North Americans, but the excretion per kg was slightly higher, suggesting that the Burmese are more muscular.