Magnesium deficiency in chronic alcoholic patients uncovered by an intravenous loading test

Magnesium sulphate (30 mmol in 1 litre NaCl solution, 154 mmol/l) was infused over 8 h i.v. in overnight fasted reference group (n = 12) and chronic alcoholics (n = 16) with normal kidney function. The magnesium excreted in the urine was measured in the 24 h urine beginning at the start of the infusion. Alcoholics excreted 1-15 mmol magnesium (median 6.4) and the reference group 18-30 (median 23.2) in the 24 h after the load. When the loading was repeated in the alcoholics (n = 7) after having received a hospital diet supplemented with 150 mmol magnesium citrate for 10 days, the elimination in the urine increased from 1-12 mmol (median 6.1) to 14-25 (median 20.8) close to the results in the reference group. The elimination in the urine was highly correlated (rs = 0.7) to the serum albumin concentration. The amount of magnesium eliminated in the urine by the reference group and the chronic alcoholic patients did not correlate with their serum concentrations of magnesium. The magnesium loading test in adults clearly separates a reference group from the magnesium deficient chronic alcoholics and can be used both for the diagnosis of magnesium deficiency and to follow the individual patient during repletion.