The concentration of Cu, Se and Zn in whole human blood and plasma was analysed by inductively coupled plasma mass spectrometry. Method involved dilution of sample by diluted nitric acid and Triton X-100 and measurement of 65Cu, 77Se and 66Zn intensities. Calibration solutions were spiked by main interferents. In order to evaluate suitability of the method for recognition of alternation of trace elements concentration, the uncertainty of results was estimated. The major part of uncertainty was due to repeatability, the other source (calibration and interferences) were found to be of lesser importance. The resulting uncertainty of concentration of mentioned trace elements is low as compared to between individual variability. Short-term (within day) and long-term (between day) variability of trace elements concentration was investigated and compared with between individual variability too. The time variability was negligible except for Zn concentration. The alternations of trace elements concentration in patients with several renal diseases were investigated. Only in case of patients in end-stage renal disease: hemodialyzed patients and patient treated by continuous ambulatory peritoneal dialysis the significant alternations were proved.