What is the normal potassium lab value range?

• A. 2.5-4.0 mEq/L
• B. 3.5-5.5 mEq/L
• C. 4.0-6.0 mEq/L
• D. 3.0-4.5 mEq/L

Answer: (B)

Potassium in the blood is tightly regulated because it directly affects how nerves and muscles, including the heart, function. The normal serum potassium range for adults is about 3.5 to 5.5 mEq/L. This window reflects the balance between dietary intake, cellular distribution (driven by factors like insulin and acid-base status), and renal excretion. Staying within this range is crucial because even small deviations can lead to serious problems like arrhythmias or muscle weakness. While some labs report 3.5–5.0 mEq/L, 3.5–5.5 mEq/L is a commonly accepted upper limit in many clinical settings, making it the best match among the options. The other ranges either lower the upper limit too much or raise the lower limit too high, excluding what is typically considered normal for many individuals.