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Hypermagnesemia

AKA: hypermagnesaemia

Evaluation and management of elevated blood magnesium in pediatric patients

Causes

  • Decreased GFR → ↓ filtration and ↓ phosphorus excretion
  • Large intake of magnesium (e.g., antacids, laxatives, IV fluids, maternal intake in newborns)

Excessive magnesium intake

  • Laxative, bowel prep
  • IV fluids
  • Supplementation

Signs and symptoms

  • Usually asymptomatic unless extremely high
  • Loss of deep tendon reflexes (DTRs)
  • Weakness
  • Cardiac dysrhythmias
  • Coma

Evaluation

  • Evaluate history for sources of excessive magnesium intake
  • Labs:
    • Kidney function

Treatment

  • Reduce intake of magnesium
  • Volume expansion and/or loop diuretics if no improvement despite reduction of intake
  • Administer calcium if severe and/or symptomatic

We recommend using the kidney.wiki kidney length calculator

Issues with the kidney length nomogram (MrNomogram[1,2]):

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    doi.org/10.1016/j.jpurol.2005.10.003 Pubmed ID 18947652

  2. Chen JJ, Pugach J, Patel M, Luisiri A, Steinhardt GF. The renal length nomogram: multivariable approach. J Urol. 2002;168(5):2149-2152.

    doi.org/10.1016/S0022-5347(05)64339-X Pubmed ID 12394745

  3. Vyas DA, Eisenstein LG, Jones DS. Hidden in plain sight: reconsidering the use of race correction in clinical algorithms. N Engl J Med. 2020;383(9):874-882.

    doi.org/10.1056/NEJMms2004740 Pubmed ID 32853499

  4. Horsfall LJ, Bondaronek P, Ive J, Poduval S. Clinical algorithms and the legacy of race-based correction: historical errors, contemporary revisions and equity-oriented methodologies for epidemiologists. Clin Epidemiol. 2025;17:647-662.

    doi.org/10.2147/CLEP.S527000 Pubmed ID 40673267