Measurement uncertainties in patient’s clinical chemistry parameters include variation in both preanalytical and analytical phases, as well as intra-individual biological variations are also observed. All laboratories have to develop tools to identify the sources of uncertainties in all phases in laboratory testing and thereby reduce uncertainty. Focusing on combined uncertainty and reducing them can improve quality of laboratory testing. In our laboratory we took one factor (i.e., Sample transportation time) in preanalytical phase & one factor (i.e., Retained sample storage temperature) in post analytical phase to begin with for measuring uncertainties in these phases. We also tried to study the impact of these uncertainties on few analytes measurements. Parameters like calcium and AST were found to be highly sensitive to the delays in sample transportation indication error in reporting of these parameters on transportation delay. Parameters like chloride and urea were found to be highly sensitive to the retesting indication no retesting or delayed testing of such parameters should not be entertained.