Hospital Admission Criteria for Hypomagnesemia
Admit patients with hypomagnesemia when they have severe deficiency (<1.2 mg/dL or <0.5 mmol/L), symptomatic manifestations (particularly cardiac arrhythmias, seizures, or tetany), or require IV magnesium replacement.
Specific Indications for Hospital Admission
Cardiac Manifestations Requiring Admission
- Patients with ventricular arrhythmias, torsades de pointes, or cardiac arrest associated with hypomagnesemia require immediate admission and IV magnesium 1-2 g bolus regardless of measured serum levels 1, 2
- Patients with non-life-threatening dysrhythmias associated with hypomagnesemia may be admitted to intermediate care units for continuous cardiac monitoring 1
- Any patient with ECG changes including prolonged PR, QRS, or QT intervals in the setting of hypomagnesemia warrants admission for monitoring 1
Neurologic Manifestations Requiring Admission
- Seizures, convulsions, or status epilepticus secondary to hypomagnesemia mandate admission with IV magnesium bolus (1.0 gm or 8.1 mEq MgSO4) 3
- Neuromuscular hyperactivity including tremor, myoclonic jerks, spontaneous carpopedal spasm, or positive Chvostek/Trousseau signs with severe hypomagnesemia (<1.2 mg/dL) 3, 4
- Altered mental status, delirium, or psychiatric disturbances attributable to magnesium deficiency 3
Severity-Based Admission Criteria
- Severe hypomagnesemia (<1.2 mg/dL or <0.5 mmol/L) with any symptoms requires admission for parenteral therapy 2, 4, 5
- Moderate hypomagnesemia requiring cardiac monitoring should be admitted to intermediate care when serum levels necessitate therapeutic intervention 1
- Asymptomatic patients with mild hypomagnesemia (>1.2 mg/dL) can typically be managed outpatient with oral supplementation 4, 5
Refractory Electrolyte Abnormalities
- Hypocalcemia unresponsive to calcium replacement requires admission for IV magnesium therapy, as hypocalcemia will not correct without addressing the underlying magnesium deficiency 1, 3, 6
- Hypokalemia that is refractory to potassium replacement mandates admission for concurrent magnesium repletion 1, 3, 6
High-Risk Clinical Scenarios
- Critically ill patients with hypomagnesemia and coexisting electrolyte abnormalities require ICU-level monitoring 7
- Patients with acute MI and hypomagnesemia should be admitted with target serum magnesium maintained above 4.0 mM/L 1
- Patients requiring continuous insulin infusion (such as diabetic ketoacidosis) with concurrent moderate electrolyte abnormalities including hypomagnesemia 1
Outpatient Management Criteria
When Admission is NOT Required
- Asymptomatic mild hypomagnesemia (>1.2 mg/dL) in patients with normal renal function can be treated with oral magnesium oxide 12-24 mmol daily 2, 4
- Patients with adequate oral intake tolerance and no cardiac or neurologic symptoms 5
- Those without refractory hypocalcemia or hypokalemia 6
Critical Pitfalls to Avoid
Do not discharge patients with symptomatic hypomagnesemia before achieving adequate repletion, as symptoms typically do not arise until serum magnesium falls below 1.2 mg/dL, indicating significant total body depletion 4. The serum level can be normal despite intracellular depletion, so clinical context matters 6.
Never administer IV magnesium without documenting adequate renal function first, as magnesium toxicity can develop rapidly in renal insufficiency 3, 4. For patients with normal renal function requiring IV therapy, the initial dose is approximately 1.0 mEq/kg on day 1, followed by 0.3-0.5 mEq/kg per day for 3-5 days 3.
Patients with gastrointestinal losses (chronic diarrhea, short bowel syndrome, continuous nasogastric suctioning) or those on medications causing renal magnesium wasting (loop diuretics, aminoglycosides, cisplatin) are at particularly high risk and warrant lower thresholds for admission 6, 5.