Background: The epidemiologic transition from communicable to non-communicable disease has become a major public health concern. Diabetes is one of the causes for the increased burden of NCD’s. Among the many complications of diabetes, hypomagnesemia is a manifestation which is overlooked. Objectives: This study was designed to assess the effect of glycaemic index on serum magnesium levels. Methods: The Observational Cross-Sectional study was conducted in the Internal Medicine, of tertiary care center of Northern India, through October 2017-September 2018, among thenewly diagnosed type II diabetes mellitus patients. Results: The mean magnesium in patients with HbA1C levels <7 % was 2.07 ± 0.125, in those with HbA1C 7-9 % was 1.94 ± 0.318 and those with HbA1C >9 % was 1.92 ± 0.286. It indicates inverse relationship between serum magnesium and HbA1C levels. Conclusion: Comparison of serum magnesium levels with glycaemic index of newly diagnosed type II diabetes mellitus patients was done with the concluded that, serum Magnesium levels decline as the HbA1Clevels increases. Based on this finding we could recommend diet rich in magnesium to avoid complications.