Diurnal variations in plasma urea of hospital patients

Morning and evening plasma urea concentrations in 72 hospital patients were compared using the paired t-test. In 43 patients with normal renal function, the evening plasma urea [39. 16 +/- 10.84 mg/dl] was slightly but significantly higher than the morning one [36.93 +/- 10.03 mg/dl]. In 29 patients with renal failure, the evening [207.77 +/- 120.77 mg/dl] and the morning [207.27 +/- 121.36 mg/dl] figures were similar. Morning collection of specimens for plasma urea estimations is generally desirable but immaterial in patients known to be in renal failure