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  • High >3.5
  • Magnesium is an effective calcium channel blocker both extracellularly and intracellularly[1]
  • Intracellular magnesium profoundly blocks several cardiac potassium channels

Clinical Features

  • Symptoms may be mild nausea and vomiting initially to diaphragmatic paralysis as the Mg concentration increases

Differential Diagnosis

  • Renal Failure
  • Lithium
  • Volume depletion
  • Rhabdo
  • IV Mg (goal in PET/eclampsia 5-7 mEq/L)
  • Massive PO intake (laxative abusers, accidental Epsom salts)
  • Magnesium enemas[2]


Mg Level Signs/Symptoms
2-3 Nausea
3-4 Somnolence
4-8 Loss of DTRs, muscle weakness
8-12 Respiratory depression
12-15 Hypotension, heart block, Cardiac Arrest, death


  • IVF (NS)
  • Furosemide 20-40mg IVP
  • CaCl 10% 5-10mL IV or Ca gluconate 10% 15-30mL IV over 5min
  • Consider HD for Mg > 8 or poor renal function

See Also


  1. Rizzo MA, Fisher M, Lock JP. Hypermagnesemic pseudocoma. Arch Intern Med. 1993;153(9):1130.
  2. Schelling Fatal hypermagnesemia. JR1. Clin Nephrol. 2000 Jan;53(1):61-5.