multi class comparison
IV Electrolyte Replacement: Potassium vs Magnesium vs Calcium — Rate, Route, Monitoring
Pushing IV potassium kills the patient. Pushing IV calcium too fast does the same. The NCLEX loves asking which electrolyte can never be given IV push and the safe infusion rates — one wrong answer choice and you've selected the lethal option.
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Side-by-side3 compared
Focus
Comparevs
Dimension
Potassium (K⁺)
Magnesium (Mg²⁺)
Calcium (Ca²⁺)
Class & mechanism
- KCl — restores intracellular cation
- MgSO₄ — cofactor, smooth-muscle relaxant
- Ca gluconate/chloride — restores Ca²⁺
Indications
- Hypokalemia
- Hypomagnesemia
- torsades de pointes
- ★Preeclampsia seizure prophylaxis
- Hypocalcemia
- Cardioprotection in hyperkalemia
Route & administration
- IV diluted via pump
- PO with food
- Central line if concentrated >10 mEq/hr
- IV infusion or IM
- Loading dose, then maintenance
- IV slow push/infusion
- CaCl: central line preferred
Key assessment
- ECG: peaked T waves = hyperkalemia
- Deep tendon reflexes + respiratory rate
- Trousseau & Chvostek signs
- Trousseau & Chvostek signs
Monitoring
- Continuous cardiac/ECG monitoring
- Verify serum level before & after
- Continuous cardiac/ECG monitoring
- Verify serum level before & after
- Continuous cardiac/ECG monitoring
- Verify serum level before & after
Adverse effects
- Phlebitis/burning at IV site
- Flushing, hypotension, drowsiness
- Bradycardia if pushed too rapidly
Toxicity / safety alert
- ★NEVER IV push — dilute & infuse via pump
- Toxicity: loss of DTRs, resp depression
- ★Mg toxicity antidote: Ca gluconate
- ★Extravasation then tissue necrosis
Contraindications & interactions
- Oliguria/renal failure
- K-sparing diuretics
- Heart block
- hold if DTRs absent
- Oliguria/renal failure
- Incompatible w/ many IVs — precipitates
- Digoxin: ↑ toxicity risk
Patient teaching
- Take oral dose with food
- Never crush ER tablets
- Report weakness or trouble breathing
- Report numbness/tingling around mouth
Class & mechanism
Potassium (K⁺)
- KCl — restores intracellular cation
Magnesium (Mg²⁺)
- MgSO₄ — cofactor, smooth-muscle relaxant
Indications
Potassium (K⁺)
- Hypokalemia
Magnesium (Mg²⁺)
- Hypomagnesemia
- torsades de pointes
- ★Preeclampsia seizure prophylaxis
Route & administration
Potassium (K⁺)
- IV diluted via pump
- PO with food
- Central line if concentrated >10 mEq/hr
Magnesium (Mg²⁺)
- IV infusion or IM
- Loading dose, then maintenance
Key assessment
Potassium (K⁺)
- ECG: peaked T waves = hyperkalemia
Magnesium (Mg²⁺)
- Deep tendon reflexes + respiratory rate
- Trousseau & Chvostek signs
Monitoring
Potassium (K⁺)
- Continuous cardiac/ECG monitoring
- Verify serum level before & after
Magnesium (Mg²⁺)
- Continuous cardiac/ECG monitoring
- Verify serum level before & after
Adverse effects
Potassium (K⁺)
- Phlebitis/burning at IV site
Magnesium (Mg²⁺)
- Flushing, hypotension, drowsiness
Toxicity / safety alert
Potassium (K⁺)
- ★NEVER IV push — dilute & infuse via pump
Magnesium (Mg²⁺)
- Toxicity: loss of DTRs, resp depression
- ★Mg toxicity antidote: Ca gluconate
Contraindications & interactions
Potassium (K⁺)
- Oliguria/renal failure
- K-sparing diuretics
Magnesium (Mg²⁺)
- Heart block
- hold if DTRs absent
- Oliguria/renal failure
Patient teaching
Potassium (K⁺)
- Take oral dose with food
- Never crush ER tablets
Magnesium (Mg²⁺)
- Report weakness or trouble breathing
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Clinical Pearl
Potassium is NEVER pushed; magnesium toxicity is reversed by calcium; all three demand telemetry — slow is safe.
Component Topics
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Go further
- TopicHyperkalemiaA potassium of 6.8 mEq/L with peaked T waves means the heart could stop in minutes. The treatment sequence you choose — and the order you choose it in — determines whether it does.
- TopicHypocalcemiaA post-thyroidectomy patient reports tingling around their mouth and fingertips. The vitals look stable — but neuromuscular crisis is minutes away if you miss the calcium…
- SimulatorFluid & Electrolyte SimulatorChange one lab. Watch the whole patient respond. Sodium, potassium, calcium, magnesium, pH and volume, all linked — with a live ECG and an IV pole where every bag runs.
- GuideThe 6 Electrolyte Relationships Every Nurse Gets Tested On (Mg–K, Ca–PO₄, pH–K and More)Why potassium will not correct until magnesium does, why calcium and phosphate move in opposite directions, how pH moves potassium and ionized calcium, why sodium is a water problem, and why low potassium makes digoxin dangerous — with the mechanism and the nursing move for each, and a simulator to break them on purpose.