Periodontitis is a disease of the supporting structures of the teeth and can cause an increase in inflammatory parameters which can affect the course and outcomes of various systemic diseases. Systemic biomarkers are indicators of biological and pathological processes in the body. They are used as a diagnostic tool to evaluate the status, course and response to the therapy of various systemic diseases. In subjects with periodontitis, there are elevated levels of leukocyte, C-reactive protein (CRP), tumor necrosis factor alpha (TNF-α), and interleukin 6 (IL-6). Since these biomarkers are major indicators of cardiovascular diseases as well, periodontitis is considered one of the risk factors. After the initial periodontal therapy, the levels of the mentioned biomarkers decreased, which resulted in improvement of clinical periodontal indicators, reduction of the risk of developing systemic diseases and a positive effect on their course and outcome. Research has shown a positive effect on diabetes control after periodontal therapy in people with periodontitis. According to the results of research by some authors, it is assumed there is a positive effect of initial periodontal therapy on the course of the disease in people with rheumatoid arthritis and anemia. Many authors report a significant decrease in systemic biomarkers after non-surgical periodontal therapy, although some of them did not notice significant differences. Further studies on a larger number of patients over a longer period are needed to confirm the extent of this effect.