Hypomagnesemia (institution ranges vary; often < 1.7–1.8 mg/dL) increases neuromuscular excitability and destabilizes myocardial conduction. Magnesium modulates calcium influx and potassium transport; when Mg²⁺ is low, patients are prone to ventricular ectopy and torsades de pointes (polymorphic VT), and potassium becomes refractory to repletion. Common causes:
- GI losses/malabsorption: diarrhea, fistulas, IBD, celiac disease, post-Whipple, chronic PPI use
- Renal losses: loop/thiazide diuretics, aminoglycosides, amphotericin B, cisplatin, tacrolimus, poorly controlled diabetes
- Inadequate intake/alcohol use disorder and refeeding
- Shifts: pancreatitis (saponification), hyperaldosteronism
Clinical clues: tremor, muscle cramps, positive Chvostek/Trousseau (via linked hypocalcemia), nystagmus, seizures, and ECG changes (prolonged QT/QTc, widened QRS, ventricular ectopy). Management priorities: 1) cardiac safety (telemetry for moderate–severe or symptomatic cases), 2) replace magnesium (PO for mild; IV for moderate–severe or symptomatic), 3) co-replete potassium if low, and 4) address the cause (diuretics, PPIs, alcohol, diarrhea).
Fast Assessment & Monitoring (bedside)
- Confirm hypomagnesemia: check Mg²⁺ (and ionized Ca²⁺, K⁺, phosphate).
- Telemetry/ECG: assess for QT prolongation, ectopy, torsades risk.
- Look for drivers: diuretics, PPI/chemo, diarrhea, alcohol use, malnutrition.
- Repletion route: PO for mild/asymptomatic and intact GI; IV for symptomatic, arrhythmias, seizures, or malabsorption.
- Trend labs: recheck Mg²⁺ (and K⁺) after replacement per facility protocol; monitor DTRs and sedation with IV therapy.
Reinforce your clinical judgment with: Hyperkalemia Care Plan, Hypokalemia Care Plan, and Hypernatremia Care Plan—plus calcium cluster pages (/223, /224, /226, /227, /228), and study helpers /184, /203, /201, /195.
Nursing Care Plans for Hypomagnesemia
Individualize goals and dosing to your facility protocols and provider orders. These NGN-style plans prioritize arrhythmia prevention and effective repletion.
Nursing Diagnosis: Risk for Decreased Cardiac Output (dysrhythmias including torsades)
| Category | Details |
|---|---|
| Related to | Prolonged repolarization and increased ventricular irritability from low Mg²⁺ |
| As evidenced by | (Risk state) QT/QTc prolongation, PVCs, ventricular tachyarrhythmias; concurrent hypokalemia |
| Desired Outcomes | Maintains stable rhythm; QTc trends toward baseline; no VT/torsades; Mg²⁺ reaches provider target within 6–24 h. |
Nursing Interventions and Rationales
| Intervention | Rationale |
|---|---|
| Place on continuous cardiac monitoring; obtain baseline and follow-up ECGs. | Detects torsades and other ventricular rhythms early; documents response to repletion. |
| Administer IV magnesium sulfate per protocol for symptomatic or significant hypomagnesemia; keep calcium gluconate available if high-dose Mg²⁺ depresses respiration. | IV Mg²⁺ stabilizes myocardium and shortens QT; monitoring prevents over-sedation and respiratory compromise. |
| Co-replete potassium if low; reassess K⁺/Mg²⁺ after each replacement cycle. | Corrects refractory hypokalemia driven by Mg²⁺ deficiency. |
Nursing Diagnosis: Risk for Electrolyte Imbalance (ongoing losses/malabsorption)
| Category | Details |
|---|---|
| Related to | Diuretic therapy, diarrhea/malabsorption, alcohol use disorder, chemotherapy, PPIs |
| As evidenced by | Recurrent low Mg²⁺, low K⁺, low Ca²⁺; poor intake; GI losses; high urine Mg²⁺ if renal wasting |
| Desired Outcomes | Mg²⁺ sustained in target range; reduced need for repeat repletion; cause addressed or mitigated. |
Nursing Interventions and Rationales
| Intervention | Rationale |
|---|---|
| Review meds (loop/thiazide diuretics, PPIs, nephrotoxic agents); collaborate on adjustments or substitutes. | Reduces renal/GI magnesium wasting. |
| Initiate PO magnesium for mild/asymptomatic cases if GI tract is functional; provide GI side-effect counseling. | Builds stores with lower toxicity risk; mitigates diarrhea/loose stools that can worsen losses. |
