Inflammatory markers are commonly used laboratory determinants of infective and inflammatory conditions, especially those used in emergency department since they are widely available, affordable, and rapidly interpreted. Therefore, we have investigated CRP values and leukocyte count as two laboratory determinants for initiation of antibiotic therapy, as well as their relative and absolute differences within the 24 hours and effect of those differences on clinical outcome. We believed it was of critical importance to investigate this correlation in the setting of emergency department since that is where most acutely ill patients will initially present, but also due to very scarce and often unclear research that has been done in this subject so far. Our study included 300 patients, with an average time between first and second CRP sample being 14 ± 6 hours, and the average time between antibiotic initiation and control CRP 11 ± 6 hours. We found no correlation between changes in values and the clinical picture of these patients, both regarding CRP and leukocyte values. This means that whether patients’ condition was declining, improving, or staying the same, CRP control values were not significantly changing respective of those conditions. Regarding CRP control values corelation with clinical outcome, analysis showed statistically significant correlation between changes in absolute and relative CRP values and decision about hospitalization, discharge, observation or change in antibiotic therapy. Second statistical significance was found in case where we compared multiple variables influencing the clinical outcome, and that was that the decision about further treatment did correlate with change in leukocyte count. Since no correlation was found in all other data analysis (for example no correlation was found between clinical picture and clinical outcome), it only proves that clinical practice relies on incorrect assumption that changes in CRP values in less than 24h can correctly direct physician’s decision on further course of treatment including, continuation or change in antibiotic therapy. We concluded that often unnecessary CRP measurements are done, without any benefit of such practice in the emergency department. CRP samples are taken randomly in a sense that within this 24-hour frame, most controls were taken within half of that time, indicating that physicians might re-check CRP levels just for their reassurance but essentially without those values influencing further treatment of the patient. We believe that data we gathered proved numerous unnecessary controls of CRP, but even more importantly that clinical decisions based on those incorrectly interpreted CRP changes, especially regarding antibiotic treatment, potentially does not benefit these patients.