Treatment: calcium gluconate 100 to 200 mg/kg IV; exchange transfusion or peritoneal dialysis in severe cases
Older children and adolescents
Iatrogenic causes: TPN errors, excessive Mg supplementation in ICU setting
Reported in pediatric case series: TPN-related hypermagnesemia mimicking septic shock (Ali et al., Pediatrics 2003)
Bowel prep toxicity: magnesium citrate or Epsom salt bowel prep in patients with unrecognized renal impairment
Dosing adjustments
Calcium gluconate 50 to 100 mg/kg IV over 5 to 10 minutes for symptomatic cases
Furosemide 1 mg/kg IV to promote renal excretion
Hemodialysis or peritoneal dialysis for severe cases or renal failure
Background
Epidemiology
Epidemiological features
Hypermagnesemia is uncommon in the general population but potentially fatal when severe
Most cases occur in the setting of renal insufficiency combined with exogenous Mg intake
Prevalence is highest in CKD patients using Mg-containing OTC products
Condition is frequently unsuspected; one series found it clinically unsuspected in 6 of 8 patients despite significant sequelae (Clark and Brown, Am J Nephrol 1992)
Elderly patients using Mg-containing laxatives represent a major at-risk population
Obstetric patients receiving IV MgSO4 represent a controlled therapeutic risk population requiring mandatory monitoring
Sporadic cases in patients with normal renal function following massive oral ingestion (Epsom salts, bowel prep) are reported but less common
Pathophysiology
Magnesium homeostasis
Approximately 50 to 60% of total body magnesium resides in bone; 1% is extracellular
Renal excretion is the primary route of magnesium elimination
Normal kidneys can excrete large Mg loads; hypermagnesemia is rare with intact renal function
CrCl < 30 mL/min markedly impairs Mg excretion
GI absorption of Mg is normally 30 to 40%; rises with large oral loads
Bowel obstruction, ileus, and mucosal injury increase absorption
Mechanisms of toxicity
Mg blocks voltage-gated calcium channels at neuromuscular junctions
Calcium directly and rapidly antagonizes Mg effects at neuromuscular junction and myocardium
Does not lower serum Mg level; provides temporary protection while elimination is achieved
Calcium gluconate is preferred for peripheral IV access; calcium chloride for central access or cardiac arrest
Effect is temporary (30 to 60 minutes); repeat dosing required until elimination is complete
Elimination strategies
Renal excretion (preferred when intact): saline plus furosemide enhances excretion
Forced diuresis can increase Mg excretion significantly in patients with adequate renal function
Dialysis (required in renal failure)
Hemodialysis rapidly and effectively removes Mg
Low Mg dialysate (0 to 0.25 mmol/l) maximizes removal gradient
CRRT for hemodynamically unstable patients; slower removal but better tolerated
Rebound hypermagnesemia
Risk exists when oral Mg tablets are retained in the GI tract
Serum Mg may rise again after initial correction if GI decontamination incomplete
Serial Mg levels at 2 to 4 hours post-treatment essential to detect rebound
ICD-10 coding
E83.41: Hypermagnesemia
Associated code for CKD if relevant: N18.4 or N18.5
Patient Discharge Instructions
copy discharge instructions
Discharge instructions for hypermagnesemia
What happened: your blood magnesium level was too high, which caused your symptoms (weakness, fatigue, low blood pressure)
What to avoid
Do not take any magnesium-containing products without your doctor's approval
Avoid magnesium-containing antacids: Maalox, Mylanta, Milk of Magnesia
Avoid magnesium-containing laxatives: magnesium citrate, Milk of Magnesia, Epsom salts
Avoid magnesium supplements (oral or IV)
If you need a laxative, use non-magnesium alternatives
Polyethylene glycol (MiraLAX) is safe
Docusate sodium (Colace) is safe
Bisacodyl (Dulcolax) is safe
Diet: magnesium-rich foods (nuts, seeds, dark chocolate, leafy greens) are rarely dangerous on their own; discuss dietary restriction only if advised by your doctor
Medications: do not restart any magnesium products unless a doctor specifically prescribes them and is aware of this event
Kidney disease: if you have kidney disease, you are at higher risk; always check with your doctor before using any OTC antacids, laxatives, or supplements
Follow-up: repeat blood test within 24 to 48 hours to confirm magnesium level has returned to normal
Return to emergency department immediately for
Worsening weakness or inability to lift arms or legs
Difficulty breathing or shortness of breath
Lightheadedness, fainting, or chest pain
Confusion, drowsiness, or difficulty staying awake
Slow or irregular heartbeat
Nausea or vomiting preventing oral intake
References
Guidelines and key sources
Primary evidence sources
Clark BA, Brown RS. Unsuspected Morbid Hypermagnesemia in Elderly Patients. American Journal of Nephrology. 1992. PMID: 1489003
Ayuk J, Gittoes NJ. Contemporary View of the Clinical Relevance of Magnesium Homeostasis. Annals of Clinical Biochemistry. 2014. PMID: 24402002
Walker P, Parnell S, Dillon RC. Epsom Salt Ingestion Leading to Severe Hypermagnesemia Necessitating Dialysis. Journal of Emergency Medicine. 2020. PMID: 32389435
Si GF et al. Case Report: Near-Fatal Hypermagnesemia Resulting From the Use of Epsom Salts in a Patient With Normal Renal Function. Frontiers in Medicine. 2024. PMID: 39021819
William JH, Richards K, Danziger J. Magnesium and Drugs Commonly Used in Chronic Kidney Disease. Advances in Chronic Kidney Disease. 2018. PMID: 29793666
Weng YM et al. Hypermagnesemia in a Constipated Female. Journal of Emergency Medicine. 2013. PMID: 22244603
Qureshi T, Melonakos TK. Acute Hypermagnesemia After Laxative Use. Annals of Emergency Medicine. 1996. PMID: 8909278
Ali A et al. Iatrogenic Acute Hypermagnesemia After TPN Infusion Mimicking Septic Shock Syndrome. Pediatrics. 2003. PMID: 12837909
Cunningham J, Rodriguez M, Messa P. Magnesium in CKD Stages 3 and 4 and in Dialysis Patients. Clinical Kidney Journal. 2012. PMID: 26069820
Oliveira B, Cunningham J, Walsh SB. Magnesium Balance in Chronic and End-Stage Kidney Disease. Advances in Chronic Kidney Disease. 2018. PMID: 29793669
Wolf MT. Inherited and Acquired Disorders of Magnesium Homeostasis. Current Opinion in Pediatrics. 2017. PMID: 27906866
Quamme GA. Renal Magnesium Handling: New Insights in Understanding Old Problems. Kidney International. 1997. PMID: 9350641
Sandau KE et al. Update to Practice Standards for Electrocardiographic Monitoring in Hospital Settings. AHA Scientific Statement. Circulation. 2017
Mosseri M et al. Electrocardiographic Manifestations of Combined Hypercalcemia and Hypermagnesemia. Journal of Electrocardiology. 1990. PMID: 2384729
Noordam R et al. Effects of Calcium, Magnesium, and Potassium Concentrations on Ventricular Repolarization. JACC. 2019. PMID: 31221261
Van Hook JW. Endocrine Crises: Hypermagnesemia. Critical Care Clinics. 1991. PMID: 2007216
Kala J, Abudayyeh A. Magnesium: An Overlooked Electrolyte. Journal of Emergency Medicine. 2017. PMID: 28222929
SymptomDx is an educational tool for medical professionals. It does not replace clinical judgment. Verify all clinical data and drug dosages with authoritative sources.