BACKGROUND: Low serum magnesium levels are related to diabetes mellitus (DM), high blood pressure (HBP) and metabolic syndrome (MS). However, as far as is known, there have been no previous studies analyzing the relevance of the serum and intracellular magnesium concentrations in diabetic microvascular complication individuals compared with healthy individuals. SUBJECTS AND METHODS: A pilot study was performed to compare 35 individuals with DM with 22 disease-free control subjects. The serum and intracellular magnesium levels of each group were measured, and found to be elevated in the diabetic group with diabetic microvascular complications. RESULTS: The mean serum magnesium levels among the subjects with DM and the control subjects were 0.0503 +/- 0.0750 and 0.9166 0.1149 mmol/L (p<0.001), respectively. The mean intracellular magnesium levels among the subjects with DM and the control subjects were 3.3548+/-0.1863 and 3.6732 0.2428 mM/mg protein (p<0.001), respectively. In those diabetic subjects whose serum magnesium concentration was measured, 28 had diabetic retinopathy, 30 diabetic nephropathy and 20 diabetic neuropathy. The mean serum magnesium concentrations of each diabetic microvascular complication were 0.9320 0.2813, 0.9259 0.1188 and 0.9305 0.1293 mmol/L, respectively, which that were significantly lower than those of the healthy subjects (p<0.001, p<0.001 and p<0.01). Also, the diabetic subjects whose intracellular magnesium concentrations were measured, 13 had diabetic retinopathy, 15 diabetic nephropathy and 9 diabetic neuropathy. The mean intracellular magnesium concentrations of each diabetic microvascular complication were 3.3484 0.1607, 3.3289 0.1832 and 3.3768 0.2096 mM/mg protein, respectively, and were also significantly lower than those of the healthy subjects (p<0.001and p<0.01). Each diabetic microvascular complication was also negatively correlated with the serum magnesium and intracellular magnesium levels. CONCLUSION: This study reveals that a significant relation ship exists between low serum and intracellular magnesium levels and diabetic microvascular complications, particularly retinopathy and nephropathy. A large scale study on these subjects will be required to generalize our results.