The introduction of new approaches to determine the patient’s condition and treatment efficacy is feasible only with adaptation responses, among which the incomplete adaptation and overactivation occupy an important place. The study of adaptation processes by adaptation index, relative content of blood lymphocytes, type of adaptation and state of its mechanisms was conducted in 1208 patients. Incomplete adaptation with flaccid inflammatory syndrome was detected in 15±4% of the set (3-30%); with a high prevalence among patients with indices of digestive (5-30%) and endocrine (3-28%) systems. An increase in its frequency after treatment of liver diseases (from 34% to 45%) may indicate an unfavorable prognosis. The frequency of detection of the overactivation reaction ranged from 0 to 12%, and it also occurred more often among gastroenterological patients (about 4%). Internal diseases had some peculiarities in these reactions: lower parameters of the function of external respiration were diagnosed in patients with bronchoconstriction; the adaptation index correlated with the main parameters of hemodynamics in cardiovascular patients; functional parameters were worse at a lower level of reactivity with changes in WBC differential in patients with chronic kidney disease. Reactions of incomplete adaptation and overactivation relate to distress and correlate with the course of inflammation, hemostasis and immune reactivity; determine severer course of the disease and functional changes in the remission stage.