Chart — Electrolytes
Magnesium Disorder Comparison Chart
Magnesium mirrors calcium: low = hyperreflexic and arrhythmic, high = reflexes fade then breathing fails. The deep tendon reflex is the bedside dial — and calcium gluconate is the rescue when it’s too high.
Educational use only. Replacement and reversal are provider-directed; IV magnesium is high-alert. This chart is an educational comparison aid. This material supports nursing education and exam review. It is not medical advice and is not a substitute for clinical judgment, institutional policy, or medical direction. Always follow facility protocols and current provider orders.
Hypomagnesemia vs Hypermagnesemia
| Feature | Hypomagnesemia | Hypermagnesemia |
|---|---|---|
| Serum magnesium | < 1.5 mg/dL | > 2.5 mg/dL |
| Excitability | Hyperexcitable | Depressed |
| Deep tendon reflexes | HYPERactive (brisk) | DECREASED / absent (early warning) |
| Causes | Alcohol use, malnutrition/refeeding, GI losses, diuretics, PPIs | Renal failure, excess Mg (antacids/laxatives, OB mag sulfate) |
| Signs/symptoms | Tremor, twitching, Chvostek/Trousseau, seizures, torsades | Flushing, hypotension, bradycardia, lethargy, respiratory/cardiac depression |
| Companion electrolytes | Often LOW K and LOW Ca (refractory until Mg fixed) | — |
| Nursing priority | IV Mg sulfate (slow, high-alert); replace K/Ca; seizure precautions; telemetry | STOP Mg sources; calcium gluconate antidote; support ventilation; dialysis if renal |
Exam Traps
- ✦Low Mg = hyperreflexia + torsades; high Mg = decreased/absent reflexes → respiratory depression.
- ✦Decreased deep tendon reflexes are the early warning of hypermagnesemia (the OB mag-sulfate check).
- ✦Calcium gluconate is the antidote for symptomatic hypermagnesemia.
- ✦Renal failure = #1 cause of high Mg; alcohol use = classic cause of low Mg.
- ✦Refractory low K or low Ca? Replace magnesium first.
Related Resources
Standards & sources
Fact-checked Jun 20, 2026This page is written to align with Infusion Nurses Society (INS) Standards of Practice · Institute for Safe Medication Practices (ISMP) · Standard laboratory reference ranges. It is an educational summary, not a citation of any single document — always verify specific doses, values, and protocols against current guidelines and your facility policy. How we source content →