Periodontitis is an infectious disease associated with a subgingival biofilm resulting in the inflammation within the supporting tissues of the teeth, progressive attachment loss, and bone loss. Periodontitis has been linked to cardiovascular diseases where many authors have suggested that chronic oral infection leads to prolonged systemic inflammation hence development of arterial atheromas . A study was performed to see the effect of full mouth disinfection on the haematological parameters and see if there is any improvement in infectious state after the periodontal therapy. It was concluded that the haematological parameters like TLC, DLC and platelet count improved from their higher range towards the lower and normal range after the periodontal therapy.