What is a normal potassium level?

Normal potassium is 3.5–5.0 mEq/L. Use your facility's reference range.

Potassium (K⁺)

Muscle weakness, cramps, Flat T waves, U waves, Arrhythmias — especially on digoxin, Ileus, constipation.

Peaked T waves → wide QRS, Muscle weakness → paralysis, Bradycardia, arrest.

Normal 3.5–5.0 mEq/L

Why it matters

Cardiac and muscle electricity. The narrowest window, the fastest kill.

LOW — Hypokalemia (< 3.5)

Causes

Loop/thiazide diureticsVomiting, diarrhea, NG suctionInsulin (shifts K into cells)Low magnesium (fix Mg first)

Signs

Muscle weakness, crampsFlat T waves, U wavesArrhythmias — especially on digoxinIleus, constipation

Nursing actions

Telemetry for significant lows
Replace per orders — NEVER IV push K; peripheral infusion typically max 10 mEq/hr on a pump (verify policy)
Check the magnesium
Extra caution if the patient takes digoxin

HIGH — Hyperkalemia (> 5.0)

Causes

Renal failureACE/ARB + K-sparing diuretic combosAcidosis (K shifts out of cells)Tissue breakdown; hemolyzed sample (false)

Signs

Peaked T waves → wide QRSMuscle weakness → paralysisBradycardia, arrest

Nursing actions

ECG/telemetry NOW for > 6.0
Hold all K sources (meds, fluids, diet)
Anticipate: calcium gluconate (protects the heart), insulin + D50 (shifts K in), kayexalate/dialysis (removes it)
Redraw if hemolysis is plausible — but treat the sick patient, not the wait

Source: Ignatavicius, Medical-Surgical Nursing, 10th ed.Reference only — verify against your facility's policy.