The Diabetes mellitus is one of the dominated disease and its focused studies are concerned to compete with this issue worldwide. Grapefruit albedo, seeds and their blends were supplemented in marmalade to evaluate their potential in controlling diabetes and developing immunity. The present study has been planned to find out the grapefruit effect on the Diabetes mellitus and immune system. Marmalades supplemented with higher albedo contents i.e. A5 (containing 5% albedo powder) and A4S1 (containing 4% albedo and 1% seed powder) exhibited higher values for TPCs, TFCs, antioxidant activity as well as satisfactory acceptance by the consumers. These marmalades were further subjected to bio efficacy trials using Sprague Dawley rats induced with diabetes. Rats were divided into 3 groups i.e. G0 (normal diet + C), G1 (normal diet + A5) and G2 (normal diet + A4S1). The G1 and G2 exhibited less weight gain with significant decrease in all biomarkers of diabetes including blood glucose level, blood insulin level and HbA1c. Moreover, an increase in red blood cells (16% and 8% in G1 and G2, respectively), hemoglobin (11% and 8.57 %), white blood cells (17% and 6%) and platelet count (1% and 0.7%) was observed. Erythrocyte sedimentation rate and C-reactive protein were decreased by 15% and 5%, respectively, compared to the rats fed with the control diet. These results reflected the potential of grapefruit albedo and seeds in combating diabetes and developing immunity through the development of value-added food products.