[Magnesium excretion in urine is not a marker of magnesium deficiency. Reliability of an oral magnesium administration test].

BACKGROUND

Serum magnesium analysis does not reflect body content of magnesium. So substitution is based on empirical maneuvers.

PATIENTS AND METHOD: In a study on 44 patients urinary magnesium excretion was analyzed before and after oral magnesium substitution (40 mval). The provable hypothesis was the estimation that patients in magnesium deficiency under chronical diuretic treatment (n = 11) would have a lower magnesium excretion than patients of the control group (n = 10). Further analysis was done with patients after orthotopic cardiac transplantation (n = 12) and those suffering from coronary heart disease (n = 11).

RESULT: After oral administration of magnesium in all 4 groups there was a rise in blood levels, only significant in the patient group under chronic diuretic treatment. Urinary magnesium excretion, however, showed no significant differences. Patients after cardiac transplantation had the lowest rise in urinary magnesium excretion.

CONCLUSION

There was no clear differentiation by means of this oral magnesium substitution test. Magnesium excretion even after oral substitution is of no value to analyze magnesium deficiency.