Dengue is one among the acute viral infections with the probability of fatal complications. In 2017; NVBDCP reported 157220 positive dengue cases with 250 deaths in India; 17018 cases and 5 deaths in Karnataka. Most primary infections are uneventful.  The critical illness like Dengue Haemorrhagic Fever and Dengue Shock Syndrome are generally attributed to serotype cross-reactivity. Identification of secondary dengue infection in the early onset of illness is beneficial. Therefore, methods to discrepate primary and secondary dengue infection are of significant prognostic value. The current study is a hospital based prospective analytical evaluation and was aimed to discriminate secondary from primary dengue virus infection in clinically suspected dengue cases presenting with fever and thrombocytopenia. Patients of all age groups attending Krishna Rajendra Hospital on outpatient and inpatient basis with clinically suspected dengue fever of less than 5 days associated with thrombocytopenia were included in the study. The samples were tested in the VRDL of the Microbiology Department for dengue NS1 antigen and IgM antibodies, positive for both were further subjected to IgG antibodies. IgM /IgG ratio was used to differentiate primary and secondary dengue infections. Dengue infection was categorized based on WHO guidelines. A total of 17,841 samples were tested from May 2017 to December 2023; out of 17841 samples tested 2111 (60.74%) were positive for dengue NS1 and IgM. Of the 2111 dengue NS1 and IgM positive cases, 1700 (80.5%) were having secondary dengue infection, whereas 411 (19.46%) were having primary infection. Early detection of secondary infection helps the clinician in anticipating dengue related complications with appropriate therapeutic intervention, thereby reducing further complications and mortality.