Guide — Electrolytes
Potassium Disorders: Hypokalemia & Hyperkalemia
Causes, clinical manifestations, ECG changes, treatment approaches, nursing interventions, and patient safety concerns for potassium imbalances — the most common electrolyte disorders in clinical nursing practice.
11 min read · Electrolytes
Educational use only. IV potassium protocols and dose thresholds vary by institution. Always follow facility policy and provider orders. Never administer IV potassium without a pump. 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.
Potassium Physiology
Normal serum potassium: 3.5–5.0 mEq/L. Potassium is the primary intracellular cation — approximately 98% of total body potassium is inside cells. Small changes in serum K⁺ reflect large total-body shifts.
Potassium is essential for cardiac and skeletal muscle cell membrane repolarization. Even small deviations from normal can produce life-threatening dysrhythmias.
- K⁺ moves INTO cells with: insulin, alkalosis, beta-2 agonists (albuterol), glucose administration
- K⁺ moves OUT OF cells with: acidosis, cell destruction, tissue breakdown, succinylcholine
- Kidneys excrete 90% of total body potassium — renal failure = hyperkalemia risk
- Aldosterone stimulates kidney K⁺ excretion — aldosterone excess = hypokalemia
Hypokalemia (K⁺ < 3.5 mEq/L)
Causes
- GI losses: vomiting (gastric acid contains K⁺), diarrhea, ileostomy, NG suction
- Renal losses: loop diuretics (furosemide), thiazide diuretics, hyperaldosteronism, Cushing's syndrome, hypomagnesemia (Mg is required for renal K⁺ conservation)
- Transcellular shift: insulin administration, alkalosis, beta-2 agonist excess
- Inadequate intake: malnutrition, eating disorders, prolonged NPO
- Medications: amphotericin B, aminoglycosides, corticosteroids, insulin overdose
Clinical Manifestations
| System | Findings |
|---|---|
| Cardiac | Flat or inverted T waves, U waves (positive deflection after T wave), prolonged QT, PVCs, atrial and ventricular dysrhythmias; potentiates digoxin toxicity |
| Musculoskeletal | Muscle weakness (legs first), cramps, fatigue; severe: flaccid paralysis, respiratory muscle weakness |
| GI | Constipation, decreased bowel sounds, paralytic ileus |
| Renal | Polyuria, polydipsia (K depletion causes nephrogenic DI) |
Treatment
| Severity | K⁺ Range | Approach |
|---|---|---|
| Mild | 3.0–3.5 mEq/L | Oral KCl (most preferred); increase dietary potassium (bananas, oranges, potatoes, leafy greens) |
| Moderate | 2.5–3.0 mEq/L | Oral KCl preferred if tolerated; IV KCl if unable to take PO |
| Severe | < 2.5 mEq/L or symptomatic | IV KCl with continuous cardiac monitoring; peripheral max 10 mEq/hr; central max 40 mEq/hr; repeat labs after each replacement dose |
Hyperkalemia (K⁺ > 5.0 mEq/L)
Causes
- Decreased renal excretion (most common): acute kidney injury, chronic kidney disease, adrenal insufficiency (Addison's)
- Medications: ACE inhibitors, ARBs, potassium-sparing diuretics (spironolactone, amiloride), NSAIDs, heparin, trimethoprim
- Transcellular shift out of cells: metabolic acidosis, cell death (hemolysis, rhabdomyolysis, tumor lysis syndrome), succinylcholine, trauma
- Excess intake: excessive IV potassium, salt substitutes, potassium supplements
- Pseudohyperkalemia: hemolyzed specimen — always repeat before treating
ECG Progression (Know This Sequence)
| Approximate K⁺ Level | ECG Change | Clinical Significance |
|---|---|---|
| 5.5–6.5 mEq/L | Peaked (tall, narrow, symmetric) T waves | First ECG change — alert provider immediately |
| 6.5–7.5 mEq/L | Prolonged PR, widened QRS | Conduction delay — emergency treatment needed |
| > 7.5 mEq/L | Sine wave pattern, loss of P waves | Imminent cardiac arrest — code situation |
| > 8.0 mEq/L | Ventricular fibrillation, asystole | Cardiac arrest |
Treatment — Sequential Priority
| Priority | Agent | Mechanism | Onset |
|---|---|---|---|
| 1st | Calcium gluconate (or calcium chloride) | Stabilizes cardiac cell membrane — does NOT lower K⁺ | Minutes |
| 2nd | Insulin (regular) + D50W | Drives K⁺ into cells; dextrose prevents hypoglycemia | 15–30 min |
| 2nd alt | Sodium bicarbonate | Corrects acidosis; drives K⁺ into cells (most effective in acidotic patients) | 30–60 min |
| 3rd | Sodium polystyrene sulfonate (Kayexalate) or patiromer | Binds K⁺ in GI tract — eliminates from the body | Hours |
| Definitive | Dialysis | Removes K⁺ from the body — most effective for renal failure | Per access |
IV Potassium Safety
- Never administer IV potassium as an IV push or bolus — cardiac arrest risk
- Always use an IV infusion pump — never gravity drip
- Peripheral line: maximum 10 mEq/hr, maximum concentration 10 mEq/100 mL (burning at site is common — warn patient)
- Central line: up to 40 mEq/hr with continuous cardiac telemetry monitoring
- Recheck potassium level after each replacement dose before administering more
- Confirm adequate urine output (≥ 30 mL/hr) before administering potassium
- Correct hypomagnesemia first — without adequate Mg²⁺, the kidneys cannot conserve K⁺ and replacement will be ineffective
NCLEX Pearls
IV K⁺ = never IV push. This is a top-5 medication error and a frequent NCLEX safety question.
Digoxin + hypokalemia = dangerous combination. Hypokalemia potentiates digoxin toxicity — monitor for bradycardia, visual changes, nausea in digoxin patients with low K.
Pseudohyperkalemia: A hemolyzed blood sample releases intracellular K and gives a falsely elevated result. Always repeat before treating if the patient has no symptoms and no ECG changes.
First drug for hyperkalemia with ECG changes: Calcium gluconate — not insulin, not bicarb. It stabilizes the cardiac membrane within minutes.
Kayexalate nursing note: Not for emergency treatment (takes hours); watch for GI complications including colonic necrosis if given to post-op patients.
Urine output before K replacement: Always verify ≥ 30 mL/hr — without adequate renal function, administered potassium cannot be excreted and may cause hyperkalemia.
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 →