In metrology, measurement uncertainty is an expression of the statistical variance of values attributed to a measured quantity. All measurements are subject to uncertainty, and the measurement result is complete only when it is accompanied by data on the uncertainty associated with it. The scientists have considered the main provisions of the current regulatory and methodological documents on the problem of accounting for uncertainty values when measuring physical factors of a non-ionizing nature and evaluating their results. In particular, the fundamental in terms of the definition and application of measurement uncertainty GOST 34100.1–2017/ISO/IEC Guide 98-3:2008 is considered in detail. The authors highlighted the issues of taking into account measurement uncertainty in the hygienic assessment of physical factors of the production environment, including the rules for evaluating measurement results taking into account uncertainty, a list of certified methods for measuring physical factors in the workplace indicating the parameters of extended uncertainty, ways to reduce uncertainty.