['Magnesium modulates insulin-mediated glucose uptake but data regarding its role in insulin secretion are scarce; therefore, in this study we determined whether decreased serum magnesium levels are associated with the impairment of insulin secretion in non-diabetic individuals.', 'A total of 182 apparently healthy subjects, men and non-pregnant women, 18-65 years of age, were enrolled in a population-based cross-sectional study and allocated to groups with hypomagnesaemia and normomagnesaemia. The groups in the study were subsequently stratified according to glucose status: normal glucose tolerance, impaired fasting glucose, and impaired glucose tolerance. Insulin secretion was evaluated by the first and second phases of insulin secretion.', 'The Spearman coefficient between serum magnesium and the first and second phases of insulin secretion showed a significant positive correlation in the overall (r = 0.265, p < 0.0005; r = 0.541, p < 0.0005), normal glucose tolerance (r = 0.369, p = 0.001; r = 0.618, p < 0.0005), impaired fasting glucose (r = 0.320, p = 0.02; r = 0.449, p = 0.001), and impaired glucose tolerance (r = 0.129, p = 0.37; r = 0.522, p < 0.0005) groups. The multivariate linear regression analysis showed a significant association between serum magnesium levels and the first and second phases of insulin secretion: for the entire groups [B = 75.2; 95% confidence interval (CI) 27.6-122.7; B = 25.4; 95% CI 16.4-34.3], normal glucose tolerance (B = 129.6, 95% CI 38.1-221.1; B = 40.3, 95% CI 23.7-56.8), impaired fasting glucose (B = 75.2, 95% CI 27.6-122.7; B = 15.1, 95% CI 4.2-30.2), and impaired glucose tolerance (B = 57.4, 95% CI 23.5-138.3; B = 25.4, 95% CI 16.4-34.3) groups.'] Is insulin secretion decreased in non-diabetic individuals with hypomagnesaemia?