A 48-year-old patient with a history of diabetes mellitus, presented to a surgical ward with abdominal pain. She was found to have hypokalemia. Her younger sister had passed away due to sudden cardiac death at the age of 25 years. Further evaluation revealed an elevated trans-tubular potassium gradient suggestive of renal potassium loss, normal blood pressure, hypomagnesemia, hypocalciuria, and alkalosis. Moreover, there was evidence of secondary hyperaldosteronism. Genetic studies revealed two heterozygous mutations of the SLC12A3 gene, including a novel mutation which has not been reported before anywhere in the world. She was treated with intravenous potassium supplementation and was later converted to oral potassium and oral magnesium supplementation with spironolactone. Her potassium and magnesium levels normalized and glycaemic control also improved. Hypokalemia and hypomagnesemia found in Gitelman syndrome may be associated with insulin resistance and correction of electrolytes can lead to better glycaemic control.