Background: The reporting interval is the incremental value chosen in reporting analyte concentration. Reporting intervals for different analytes are often inappropriately narrow, when analytical imprecision and biological variability are considered. Methods: We have used statistical techniques to determine intervals for individual analytes at which there is 50% or 95% confidence that two results are analytically different, and compared these with the reporting intervals in use for a range of general chemistry analytes and analytes usually measured by immunoassay. Results: No analytes met the criteria for 95% confidence that the results are analytically different. Even at the 50% confidence level, 24 of 46 analytes failed at all concentrations examined. For some analytes, particularly hormones at high concentration, the reporting interval increment should be increased by a factor of at least ten. Conclusions: The majority of analytes are inappropriately reported when analytical precision alone is considered. The concept of the 'uncertainty of measurement' has not been adequately addressed. A consensus should be reached and implemented on appropriate reporting intervals for all analytes.