Chart — Electrolytes
Electrolyte Abnormality Comparison Chart
Side-by-side comparison of low and high states for four key electrolytes — sodium, potassium, calcium, and magnesium — with causes, clinical findings, ECG considerations, and nursing priorities.
Educational use only. Electrolyte abnormalities require laboratory confirmation and provider notification before treatment. Critical values require immediate provider notification. Always follow institutional protocols. 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.
Sodium (Na⁺) — Normal: 136 – 145 mEq/L
| Hyponatremia (< 136) | Hypernatremia (> 145) | |
|---|---|---|
| Key Causes | SIADH, diuretics, HF, cirrhosis, vomiting, excess free water | Dehydration, DI, fever/sweating, insufficient water intake |
| Brain Effect | Water moves INTO cells → brain swells | Water moves OUT of cells → brain shrinks |
| Symptoms | Headache, nausea, confusion, seizures, coma | Thirst, dry mucosa, agitation, confusion, seizures |
| ECG | No specific ECG changes | No specific ECG changes |
| Key Treatment | Fluid restriction (SIADH); hypertonic saline (severe) | Free water replacement (D5W or 0.45% NaCl) |
| Correction Rate | Max 8–10 mEq/L per 24 hr (ODS risk) | Max 10 mEq/L per 24 hr (cerebral edema risk) |
Potassium (K⁺) — Normal: 3.5 – 5.0 mEq/L
| Hypokalemia (< 3.5) | Hyperkalemia (> 5.0) | |
|---|---|---|
| Key Causes | Vomiting, diarrhea, diuretics, alkalosis, insulin, poor intake | Renal failure, acidosis, ACE/ARB, potassium-sparing diuretics, crush injury |
| Symptoms | Muscle weakness, cramps, fatigue, constipation, polyuria | Muscle weakness, paresthesias, nausea, bradycardia, paralysis (severe) |
| ECG Changes | Flattened/inverted T waves, prominent U waves, ST depression, prolonged QU interval | Peaked (tall, narrow) T waves → widened QRS → sine wave → VF/PEA |
| Key Treatment | K⁺ replacement (oral preferred if tolerated); IV for severe; correct concurrent hypoMg²⁺ | Ca gluconate (stabilize) → insulin/glucose (shift) → Kayexalate/dialysis (remove) |
| Critical Values | < 2.5 mEq/L | > 6.5 mEq/L (or any ECG changes) |
Calcium (Ca²⁺) — Normal Total: 8.5 – 10.5 mg/dL
| Hypocalcemia (< 8.5) | Hypercalcemia (> 10.5) | |
|---|---|---|
| Key Causes | Hypoparathyroidism, post-thyroidectomy, vitamin D deficiency, pancreatitis, alkalosis, hypoMg²⁺ | Hyperparathyroidism, malignancy (bone mets/PTHrP), prolonged immobility, vitamin D toxicity, thiazides |
| Classic Signs | Chvostek's sign (facial twitch), Trousseau's sign (carpal spasm), tetany, perioral tingling, seizures, laryngospasm | “Bones, stones, groans, psychic moans” — bone pain, kidney stones, constipation, confusion/depression |
| ECG Changes | Prolonged QT interval (risk: torsades de pointes) | Shortened QT interval, bradycardia, heart block |
| Key Treatment | IV calcium gluconate (symptomatic); oral Ca + vitamin D (mild) | IV NS hydration; loop diuretics; bisphosphonates (malignancy); treat cause |
Magnesium (Mg²⁺) — Normal: 1.7 – 2.2 mg/dL
| Hypomagnesemia (< 1.7) | Hypermagnesemia (> 2.2) | |
|---|---|---|
| Key Causes | Alcoholism, malnutrition, diarrhea, diuretics, DKA treatment, long-term PPIs | Renal failure, excessive replacement, antacid/laxative overuse, eclampsia treatment overdose |
| Symptoms | Tremors, twitching, tetany, seizures, refractory hypoK⁺ and hypoCa²⁺, Chvostek's/Trousseau's | Flushing, nausea, decreased reflexes (patellar reflex loss = warning), respiratory depression, bradycardia, cardiac arrest |
| ECG Changes | Prolonged QT, torsades de pointes (ventricular arrhythmia) | Prolonged PR, widened QRS, bradycardia, heart block (severe) |
| Key Treatment | IV or oral magnesium replacement; correct concurrent hypoK⁺ and hypoCa²⁺ | Calcium gluconate (antidote); hold Mg sources; furosemide; dialysis (severe) |
| Clinical Key | Causes refractory hypokalemia — replace Mg first | Monitor patellar reflex — loss precedes respiratory arrest |
Related Resources
Standards & sources
Fact-checked Jun 20, 2026This page is written to align with ANA / NANDA Clinical Standards. 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 →