The purpose of the research is to develop a method for assessing the level of nonspecific protection of the human body according to indicators characterizing the adaptation processes, the use of which in the decisive rules of forecasting and diagnosis of diseases ensures an improvement in the quality of decisions made.Methods. Numerous sources have a fairly detailed description of the protective mechanisms of the human body, implemented by non-specific and specific protection systems, which are closely related to such concepts as: adaptive potential, adaptive reserve, functional state and functional reserve. The paper investigates the use of indicators characterizing the adaptive potential and adaptive reserves for quantifying the nonspecific level of protection of the body from the effects of heterogeneous external factors. The methodology of synthesis of hybrid fuzzy decision rules is used as a basic mathematical apparatus.Results. The paper shows that to quantify the level of protection of the body, it is advisable to use an indicator of the activity of regulatory systems, adaptive potential, an indicator characterizing the immune-endocrine component of adaptation and an indicator characterizing the neuropsychic component of adaptation. For this system of indicators, a method has been developed to assess the level of protection based on basic indicators characterizing adaptation processes at the system-wide level, characterized by taking into account components characterizing various mechanisms for the formation of adaptive potential and adaptive reserve, taking into account the specifics of the data structure and ways of processing them for the best results in terms of quality and time of decisions. Fuzzy functions of the level of protection according to the selected system of indicators with an integral assessment of the level of protection of the body are obtained.Conclusion. The paper shows that in order to improve the quality of forecasting and diagnosis of socially significant and occupational diseases, it is advisable to use indicators of the level of protection of the body determined by adaptive mechanisms. It is established that the quality of decision–making using the proposed models increases by 10-15%, depending on the type of tasks being solved, compared with models that do not use indicators of the level of protection of the body.