ABSTRACT Introduction: To compare the hematological parameters, serum calcium, serum iron, and TIBC levels between gastrointestinal cancer patients and healthy control participants before and after treatment. Material & Methods: The study was carried out at SMS Medical College and Hospital Jaipur, India, in the Biochemistry Department in collaboration with the Radiotherapy and Oncology Department. ESR, Hb, TRBC, WBC, Platelet, serum Calcium, Iron and TIBC levels were evaluated in 150 patients with gastrointestinal cancer before and after therapy and in healthy control participantsusing specified inclusion and exclusion criteria. The serum Calcium, Iron and TIBC levels were estimated in the biochemistry lab using an auto analyzer, and the Hematological parameters were estimated from an automated hematology analyzer in the pathology lab. The t-test was used to assess the significance of the variance in the mean values of the observed parameters between study groups. When assessing the data, p-values less than 0.05 were considered significant. Results: Our findings of gastrointestinal cancer patients revealed an increase in ESR and WBC count and a decrease in Hb, TRBC, and Platelets counts compared to healthy control subjects. Significantly lower serum Iron concentration, significantly higher serum Calcium and Total Iron Binding Capacity were seen in cancer patients compared to healthy control participants. Conclusion: Significantly high or low values of the aforementioned test parameters can have serious consequences and delay the initiation of the subsequent phase of therapy. Risk of numerous complications can be decreased with regular monitoring.