| Download the amazing global Makindo app: ✅ Means NICE/National Guidelines 2026 compliant Android | Apple | |
|---|---|
| MEDICAL DISCLAIMER: Educational use only. Not for diagnosis or management. See below for full disclaimer. |
Hypermagnesaemia
⚠️ High serum magnesium levels can induce cardiorespiratory arrest and coma. Early recognition and treatment are critical.
📖 Definition
- Serum magnesium: >1.05 mmol/L (2.6 mg/dL).
- Symptoms usually develop when plasma magnesium >2–4 mmol/L.
- Treatment indicated if Mg >6 mmol/L or if symptomatic.
| 🚨 Severe Hypermagnesemia with Symptoms |
|---|
|
| Approx. Serum Magnesium (mmol/L) | Features of Hypermagnesemia |
|---|---|
| 2 – 3.5 | 😊 Flushing, ECG changes, nausea, vomiting |
| 4 – 5 | 😴 Drowsiness, slurred speech, hypotension, absent reflexes, dizziness |
| >6 | 🪫 Muscle paralysis, respiratory depression, coma |
| >8 | 💔 Cardiac arrest |
🩺 Causes
- Adrenal insufficiency (Addison’s), CKD, AKI
- 💊 Excess magnesium laxatives/antacids
- 💉 Dialysis with high Mg dialysate
- Excess oral or IV Mg intake
- Metabolic causes: tumour lysis, DKA
- Renal failure, hypercalcaemia
- Electrolyte/Endocrine: hyperkalaemia, hypoPTH, hypothyroidism
- Other: lithium toxicity, haemolysis, rhabdomyolysis
🧑⚕️ Clinical Features
- 💪 Weakness + hyporeflexia → narcosis
- 🫁 Respiratory paralysis
- ❤️ Cardiac conduction defects → cardiac arrest at >6–8 mmol/L
📊 Toxicity Levels
- 2.5–5.0: ECG changes (widened QRS)
- 4.0–5.0: ↓ deep tendon reflexes
- >5.0: Loss of reflexes
- >7.5: Heart block, resp paralysis, CNS depression
- >12.0: Cardiac arrest
🔬 Investigations
- U&E + eGFR → assess renal function
- 📈 ECG: ↑ PR, widened QRS, tall T waves
🛠️ Management
- 🔄 ABC: Stop Mg therapy (often sufficient in mild cases).
- 💉 Calcium gluconate 10–20 mL of 10% IV (protects heart, temporary effect).
- 🍬 Glucose + insulin can lower Mg (like hyperkalaemia Rx).
- 💊 Loop diuretics (furosemide) if renal function intact.
- 🩺 Dialysis in severe kidney disease or refractory cases.
💡 Pearls
- Always check renal function when Mg is high.
- Calcium gluconate stabilises myocardium but does not lower Mg.
- Hypermagnesaemia is rare but life-threatening – usually iatrogenic (laxatives, infusions).
- Think of it when you see absent reflexes + bradycardia in a patient on Mg therapy (e.g. eclampsia).
📚 References
| The content on this website is provided for educational and informational purposes only to support exam preparation (e.g., MLA, MRCP, USMLE) and learning. This is NOT medical advice, diagnosis, treatment, or professional guidance. It does not replace consultation with a qualified healthcare professional, official guidelines (e.g., NICE, GMC, BNF), or supervised clinical practice. Always verify information with current, authoritative sources. Makindo and its contributors accept no liability for any reliance on this content, including errors, omissions, or any resulting harm, loss, or consequences. By using this site, you agree to these terms. |
|
|
Categories
- A Level
- About
- Acute Medicine
- Anaesthetics and Critical Care
- Anatomy
- Anatomy and Physiology
- Biochemistry
- Book
- Cardiology
- Collections
- CompSci
- Crib Sheets
- Dental
- Dermatology
- Differentials
- Drugs
- ENT
- Education
- Electrocardiogram
- Embryology
- Emergency Medicine
- Endocrinology
- Ethics
- Foundation Doctors
- GCSE
- Gastroenterology
- General Practice
- Genetics
- Geriatric Medicine
- Guidelines
- Gynaecology
- Haematology
- Hepatology
- Immunology
- Infectious Diseases
- Infographic
- Investigations
- Lists
- MRCP
- Mandatory Training
- Medical Students
- Microbiology
- Nephrology
- Neu
- Neurology
- Neurosurgery
- Nutrition
- OSCE
- OSCEs
- Obstetrics
- Obstetrics Gynaecology
- Oncology
- Ophthalmology
- Oral Medicine and Dentistry
- Orthopaedics
- Paediatrics
- Palliative
- Pathology
- Pharmacology
- Physiology
- Procedures
- Psychiatry
- Public Health
- Radiology
- Renal
- Respiratory
- Resuscitation
- Revision
- Rheumatology
- Statistics and Research
- Stroke
- Surgery
- Toxicology
- Trauma and Orthopaedics
- USMLE
- Urology
- Vascular Surgery