Hypermagnesemia

Last updated: January 23, 2023

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Hypermagnesemia is an electrolyte disorder in which serum magnesium levels are above the reference range. The most common cause is renal insufficiency in combination with increased magnesium intake (e.g., from laxatives). Other causes include magnesium therapy, hypothyroidism, and rhabdomyolysis. Mild hypermagnesemia is often asymptomatic but higher magnesium levels (e.g., above 4–5 mg/dL) can cause neuromuscular, gastrointestinal, and cardiovascular symptoms, including ECG abnormalities. In very severe cases, hypermagnesemia can lead to cardiac arrest and death. Concomitant electrolyte imbalances (e.g., hypocalcemia) should be assessed, as they may worsen symptoms. The most important treatment step is the discontinuation of magnesium intake, which is sufficient for most asymptomatic or stable patients. Symptomatic patients may be treated with IV isotonic fluids, IV calcium, and loop diuretics. Acute dialysis should be considered in severe cases.

Hypermagnesemia is a serum magnesium concentration above 2.2–2.4 mg/dL (0.91–1.0 mmol/L). [1][2]

Renal insufficiency in combination with increased magnesium intake (e.g., from laxatives) is the most common cause of hypermagnesemia.

Mild hypermagnesemia is often asymptomatic; symptoms typically occur if magnesium levels are above 4–5 mg/dL. [1][5]

Because most of the total magnesium in the body is located intracellularly, serum magnesium levels may not accurately reflect total body magnesium levels, and symptoms may not correlate with specific serum levels. [1][4]

Very high magnesium levels (e.g., ≥ 10 mg/dL) may lead to respiratory failure, heart block, and/or cardiac arrest! [1]

Laboratory studies [1][4]

Hypocalcemia may worsen symptoms of hypermagnesemia because calcium usually antagonizes the effects of magnesium. [7]

ECG [1]

ECG changes are usually seen if magnesium levels are > 7 mg/dL. Findings are nonspecific and may include: [4]

Supportive care[1][2][4]

Medical therapy [1][2][4]

May be indicated in patients with significant (e.g., above 6–7 mg/dL) and/or symptomatic hypermagnesemia

Prevention is key in hypermagnesemia. Caution should be used in all patients treated with magnesium-containing medication, especially those with renal insufficiency.

  1. Jameson JL, Fauci AS, Kasper DL, Hauser SL, Longo DL, Loscalzo J. Harrison's Principles of Internal Medicine, Twentieth Edition (Vol.1 & Vol.2). McGraw-Hill Education / Medical ; 2018
  2. Askew JW, Chareonthaitawee P, Arruda-Olson AM. Selecting the optimal cardiac stress test. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. https://www.uptodate.com/contents/selecting-the-optimal-cardiac-stress-test.Last updated: December 16, 2015. Accessed: February 20, 2017.
  3. Walls R, Hockberger R, Gausche-Hill M, Erickson TB, Wilcox SR. Rosen's Emergency Medicine 10th edition- Concepts and Clinical Practice E-Book. Elsevier Health Sciences ; 2022
  4. Topf JM, Murray PT. Hypomagnesemia and Hypermagnesemia.. Rev Endocr Metab Disord. 2003; 4 (2): p.195-206. doi: 10.1023/a:1022950321817 . | Open in Read by QxMD
  5. Zoungas S, Patel A, Chalmers J, de Galan BE, Li Q, Billot L, Woodward M, Ninomiya T, Neal B, MacMahon S, Grobbee DE, Kengne AP, Marre M, Heller S; ADVANCE Collaborative Group. Severe Hypoglycemia and Risks of Vascular Events and Death. N Engl J Med. 2010; 363 (15): p.1410-1418. doi: 10.1056/nejmoa1003795 . | Open in Read by QxMD
  6. Qazi M, Qazi H, Nakhoul G, Provenzano LF. Causes of Hypermagnesaemia: A Literature Review. EMJ Nephrol. 2021 : p.107-115. doi: 10.33590/emjnephrol/21-00033 . | Open in Read by QxMD
  7. Swaminathan R. Magnesium metabolism and its disorders.. Clin Biochem Rev. 2003; 24 (2): p.47-66.

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