title: The magnesium load test: experience in elderly subjects.
abstract: While serum magnesium is the simplest and most widely used approach to the evaluation of magnesium status, it is recognized that a normal serum level can occur in the presence of tissue depletion. The magnesium load test is a reliable indirect method of assessing whole body magnesium status, but experience with its use in older subjects is limited. The initial aim was to establish a range of results for the magnesium load test in older subjects who were likely to be tissue depleted. Such data would enable more accurate interpretation of the test in older subjects with normal serum levels who might be tissue-magnesium depleted. Magnesium loading was performed in 43 female subjects, average age 83 years, with serum magnesium levels not exceeding 0.75 mmol/l (mean 0.63 +/- 0.09 mmol/l) and lower than recommended dietary magnesium intakes. Magnesium sulphate was given intravenously, 0.25 mmol magnesium/kg body weight at a rate of 2.5 mmol/hour. Twenty-four-hour urine magnesium was determined for two days before the test and on the day of test from the start of the infusion. The test was abandoned in 13 other subjects because it was not possible to obtain three consecutive accurate urine collections despite careful selection. In the remaining 30 subjects, average magnesium retention was 62% (range 15-98%). Serum magnesium appeared a better guide to tissue status than urine magnesium, but creatinine clearance correlated better with the degree of magnesium retention than either serum or urine magnesium levels.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Geriatric Medicine, Glasgow Royal Infirmary Group, Lightburn Hospital, Scotland, U.K.
authors.forename: B J
authors.initials: BJ
authors.lastname: Martin
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000378:metabolism*; D003404:Creatinine / Q000652:urine; D005260:Female; D006801:Humans; D008274:Magnesium / Q000097:blood / Q000378:metabolism* / Q000652:urine
chemical_list: D003404:Creatinine; D008274:Magnesium