Hyperglycaemia enhances renal magnesium excretion in Type 1 diabetic patients

Magnesium depletion is a common feature of diabetes mellitus, apparently re lated to glycaemic control. The aim of the study was to investigate the iso lated effect of hyperglycaemia upon renal magnesium excretion. Urinary magn esium excretion rates were measured in 10 patients with Type 1 diabetes mel litus on two different days with different levels of blood glucose concentr ation but equal plasma insulin concentration. On a hyperglycaemic day, an i .v. infusion of 20% glucose was started at the end of a euglycaemic baselin e period, increasing blood glucose concentration from 5.3 mmol/L to 12.3 mm ol/L. There was no major glucosuria. On the hyperglycaemic day the renal ma gnesium excretion and clearance were raised by a factor of 2.4 compared to the euglycaemic day. Plasma magnesium concentration decreased 3% during hyp erglycaemia. In conclusion, blood glucose excursions influence magnesium ho meostasis independently of insulin levels in Type 1 diabetic patients. This effect is primarily due to an increased renal magnesium clearance during h yperglycaemia.