Evaluation and treatment of hypomagnesemia
- Alan S L Yu, MB, BChir
Alan S L Yu, MB, BChir
- Harry Statland and Solon Summerfield Professor of Medicine
- University of Kansas Medical Center
Most of the body's magnesium stores are intracellular, principally within bone. In the extracellular fluid, magnesium can be ionized (free), bound to anions, or bound to protein. (See "Regulation of magnesium balance".)
The plasma magnesium concentration is not usually measured as part of routine blood tests. Thus, the identification of patients with hypomagnesemia often requires clinical suspicion in patients with risk factors for hypomagnesemia (eg, chronic diarrhea, proton pump inhibitor therapy, alcoholism, diuretic use) or with clinical manifestations of hypomagnesemia (eg, unexplained hypocalcemia, refractory hypokalemia, neuromuscular disturbances, ventricular arrhythmias) [1,2]. (See "Causes of hypomagnesemia" and "Clinical manifestations of magnesium depletion".)
This topic will review the evaluation and treatment of hypomagnesemia. The regulation of magnesium balance, and the causes and clinical manifestations of hypomagnesemia are presented in detail elsewhere. (See "Regulation of magnesium balance" and "Causes of hypomagnesemia" and "Clinical manifestations of magnesium depletion".)
In patients diagnosed with hypomagnesemia, the cause can usually be obtained from the history. (See "Causes of hypomagnesemia".)
If no etiology is apparent, the distinction between gastrointestinal and renal losses can be made by measuring the 24-hour urinary magnesium excretion or the fractional excretion of magnesium on a random urine specimen.
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- Normomagnesemic magnesium depletion
- Patients with severe symptoms
- - Inefficiency of intravenous magnesium supplementation
- Patients with no or minimal symptoms
- - Oral repletion if available and tolerable
- - Intravenous repletion in stable hospitalized patients
- Correction of the underlying disease
- Treating patients with impaired renal function
- Duration of therapy
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