According to the results, it was found that the serum beta-lactamase activity level is determined by phenotypic and clinical variables: age over 60 years, severe respiratory pathology, fever over 380 , peripheral blood leukocyte level over 10x109, C-reactive protein over 40 mg/L and saturation less than 93%, correlating with an increase in UAV levels, and are predictors of low efficacy of treatment with beta-lactam antibiotics. A direct correlation was revealed between the level of serum beta-lactamase activity and the duration of antimicrobial therapy during the year (r=+0.86, p=0.001), the number of antimicrobial drugs prescribed simultaneously (r=+0.69, p=0.001), the fact of receiving beta-lactam reserve antibiotics – cefepime, imipenem, meropenem (r=+0.71, p=0.001), the fact of prescribing reserve antibiotics not related to the beta-lactam series – rifampicin, azithromycin, vancomycin, linezolid, levofloxacin (r=+0.59, p=0.001). Predicting the effectiveness of successful treatment with antibacterial drugs of the first-line beta-lactam group in the framework of evidencebased medicine, the need to determine the level of beta-lactamase activity of biological substrates is justified. Assessment of the level of betalactamase activity before the start of antibiotic therapy will reduce the unjustified use of beta-lactam antibiotics by up to 30%.