Background: Diabetes mellitus is a heterogeneous group of metabolic disorders characterized by chronic hyperglycemia with disturbance of carbohydrate, fat and protein metabolism resulting from defects in insulin secretion, insulin action or both. The aim of this study was to estimate serum magnesium levels in patients with type 2 diabetes mellitus and correlate it with complications of type 2 diabetes mellitus - glycemic control and retinopathy.Methods: A cross-sectional study of 100 patients with type 2 diabetes, attending Government Medical College and associated Hospital, Jammu over a period of one year from 1st November, 2014 to 30th October, 2015. Detailed history including duration of diabetes, treatment mode, symptoms suggestive of retinopathy and associated diseases such as hypertension and ischemic heart disease were obtained, as per the proforma, followed by physical examination.Results: Majority of patients (38%) of type-2 diabetes mellitus were in the age group of 51-60 years. Males constituting 71% with male to female ratio of 2.45:1. Complications were observed in 48 cases, which mainly included retinopathy 60.42% (all non-proliferative). Maximum patients (79%) had abnormal (>6.5%) glycosylated hemoglobin levels ranging from 6.5 to 12%. Patients with diabetic retinopathy had significantly higher prevalence of hypomagnesaemia compared to patients without retinopathy (58.62 % vs 18.31%).Conclusions: Prevalence of hypomagnesaemia in type 2 diabetes was 30% in the present study. The present study illustrates that as the magnesium level decreases in type 2 diabetes mellitus patients, prevalence of retinopathy increases.