Hypermagnesemia
Hypermagnesemia is a serum magnesium level above 2.4 mg/dL, almost always caused by excess magnesium intake in the setting of reduced kidney function. Mild cases are managed by stopping magnesium sources and enhancing renal excretion, while symptomatic disease needs immediate intravenous calcium gluconate followed by hemodialysis.
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What this article covers
- Overview
Elevated serum magnesium from failure to excrete an excess load: hypermagnesemia is defined by a serum magnesium level 2.4 mg/dL (0.99 mmol/L), and it occurs infrequently because the kidney normally excretes magnesium efficiently.
- Epidemiology
Uncommon compared with hypomagnesemia: hypermagnesemia occurs far less frequently than hypomagnesemia in hospitalized patients, in contrast to hypomagnesemia's roughly 20% incidence.
- Risk factors
Reduced kidney function: advanced CKD or acute kidney injury impairs the renal magnesium excretion that normally prevents accumulation from dietary or medicinal intake.
- Pathophysiology
Normal magnesium handling depends on renal excretion: of the ideal daily intake of 350-450 mg, the kidney filters and reabsorbs magnesium so that about 100 mg is excreted in the urine daily when…
- Clinical features
Loss of deep tendon reflexes is the earliest sign: it typically appears once serum magnesium exceeds 4.8 mg/dL (1.98 mmol/L) and precedes more severe neuromuscular findings.
- Differential diagnosis
Opioid or sedative toxicity: produces lethargy and respiratory depression but preserves deep tendon reflexes early, unlike hypermagnesemia, and improves with naloxone or flumazenil rather than calcium.
- Diagnosis
The diagnosis is confirmed by an elevated serum magnesium level; severity is graded by the presence of neuromuscular or cardiovascular findings rather than the number alone, though clinically…
- Management
First, stop every magnesium-containing source: discontinue magnesium-containing antacids, laxatives, and any magnesium sulfate infusion immediately in every patient with hypermagnesemia.
- Complications
Respiratory failure from flaccid paralysis: involvement of respiratory muscles can require mechanical ventilation if hypermagnesemia is not corrected promptly.
- Prognosis
Excellent with prompt recognition and treatment: most cases resolve completely once the magnesium source is stopped and, when needed, excretion is enhanced or dialysis is performed.
- Prevention
Avoid magnesium-containing antacids and laxatives in patients with an estimated glomerular filtration rate (GFR) <30 mL/min/1.73 m2 or known advanced CKD; recommend non-magnesium alternatives (for…
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- Hypocalcemia
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- Renal replacement therapy
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- Hypomagnesemia
Hypomagnesemia is a serum magnesium level below 1.7 mg/dL, most often caused by gastrointestinal losses, proton pump inhibitors, or renal magnesium wasting from diuretics and other drugs. It causes concurrent hypokalemia and hypocalcemia and can potentiate cardiac arrhythmias, and treatment is intravenous magnesium sulfate for significant symptoms or slow-release oral repletion for milder deficiency.
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- Hyperkalemia
Hyperkalemia is a serum potassium level above 5.0 mEq/L, most often from decreased kidney excretion, transcellular shifts, or excess intake, with levels above 6.0-6.5 mEq/L or any ECG change constituting a medical emergency from the risk of fatal arrhythmia. Treatment sequences cardiac membrane stabilization with calcium, transcellular potassium shifting with insulin/dextrose and albuterol, then definitive potassium removal with binders, diuretics, or dialysis.