The effect of magnesium supplements on early post-transplantation glucose metabolism: a randomized controlled trial

Post-transplantation hypomagnesemia is common and predicts diabetes. Magnesium improves glycemic control in diabetics and insulin sensitivity in insulin resistant subjects. We aimed to assess the effectiveness of oral magnesium for improving glycemic control and insulin sensitivity at 3 months post-transplantation. We conducted a single-center, open-label, randomized parallel group study. We included adults with serum magnesium <1.7 mg/dl within 2 weeks after kidney transplantation. We randomized participants to 450 mg magnesium oxide up to three times daily or no treatment. The primary endpoint was the mean difference in fasting glycemia. Secondary endpoints were the mean difference in area under the curve (AUC) of glucose during an oral glucose tolerance test and insulin resistance measured by Homeostasis Model of Assessment-Insulin Resistance (HOMA-IR). Analyses were on intention-to-treat basis. In patients randomized to magnesium oxide (N = 27) versus no treatment (N = 27), fasting glycemia on average was 11.5 mg/dl lower (95% CI 1.7 to 21.3; P = 0.02). There was no difference between the two groups neither for 2 h AUC, where the mean value was 1164 mg/dl/min (95% CI -1884 to 4284; P = 0.45) lower in the treatment group nor for HOMA-IR. Magnesium supplements modestly improved fasting glycemia without effect on insulin resistance. Higher baseline glycemia among patients in the control group may have driven the positive outcome (ClinicalTrials.gov number: NCT01889576).