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Magnesium Imbalances: Causes and Manifestations

Magnesium

  • Roles of Magnesium
    • Coenzyme in metabolism of carbohydrates
    • Required for DNA and protein synthesis
    • Blood glucose control
    • BP regulation
    • Necessary for ATP production
    • Acts directly on myoneural junction
    • Important for normal cardiac function
    • 50% to 60% contained in bone
    • Absorbed in GI tract
    • Excreted by kidneys
  • Hypermagnesemia
    • High serum Mg caused by
      • Increased intake or ingestion of products containing magnesium when renal insufficiency or failure is present
      • Excess IV magnesium administration
    • Manifestations
      • Lethargy
      • Nausea and vomiting
      • Impaired reflexes
      • Muscle paralysis
      • Respiratory and cardiac arrest
      • Urinary retention
      • Flushed, warm skin, especially facial
      • Decreased Pulse, Decreased BP
    • Management
      • Prevention first—restrict magnesium intake in high-risk patients
      • IV CaCl or calcium gluconate if symptomatic
      • Fluids and IV furosemide to promote urinary excretion
      • Dialysis
  • Hypomagnesemia
    • Low serum Mg caused by
      • Prolonged fasting or starvation
      • Chronic alcoholism
      • Fluid loss from gastrointestinal tract
      • Prolonged parenteral nutrition without supplementation
      • Diuretics
      • Hyperglycemic osmotic diuresis
    • Manifestations
      • Hyperactive deep tendon reflexes
      • Muscle cramps
      • Tremors
      • Seizures and confusion
      • Cardiac dysrhythmias
      • Corresponding hypocalcemia and hypokalemia
      • Chvostek’s and Trousseau’s signs
      • Increased Pulse, Increased BP, dysrhythmias
    • Management
      • Treat underlying cause
      • Oral supplements
      • Increase dietary intake
      • Parenteral IV or IM magnesium when severe

Magnesium Imbalances: Causes and Manifestations

Hypermagnesemia (Mg+ >2.5 mEq/L [1.25 mmol/L])

Hypomagnesemia (Mg+ <1.5 mEq/L [0.75 mmol/L])

Cause

  • Renal failure
  • GI tract fluid losses (e.g., diarrhea, NG suction)
  • IV administration of magnesium, especially for treatment of eclampsia
  • Chronic alcoholism
  • Tumor lysis syndrome
  • Malabsorption syndromes
  • Hypothyroidism
  • Prolonged malnutrition
  • Metastatic bone disease
  • Increased Urine output
  • Adrenal insufficiency
  • Hyperglycemia
  • Antacids, laxatives
  • Proton pump inhibitor therapy