What is the critical range for potassium?

• A. 2.0-5.0 mg/dL
• B. 2.5-6.5 mg/dL
• C. 3.0-7.0 mg/dL
• D. 1.5-4.5 mg/dL

Answer: (B)

Potassium is tightly linked to heart rhythm, so doctors treat values outside a narrow window as urgent. The reason a specific range is used as the critical alert range is that it marks when potassium could cause life‑threatening arrhythmias if not addressed promptly. Values below about 2.5 (hypokalemia) raise the risk of dangerous muscle weakness and irregular heartbeats, while values above about 6.5 (hyperkalemia) can lead to severe conduction problems and potentially fatal rhythms. Therefore, the range 2.5 to 6.5 captures the concentrations at which urgent clinical intervention is typically warranted. Other ranges either miss values that require rapid action or extend beyond the practical, safe alert threshold, making them less appropriate for signaling urgent potassium abnormalities.