What is the normal range of potassium in the body?

• A. 1.5 to 3.0 mEq/L
• B. 3.5 to 5.0 mEq/L
• C. 5.5 to 7.0 mEq/L
• D. 0.5 to 2.0 mEq/L

Answer: (B)

Potassium must be kept within a narrow window to preserve normal electrical activity of nerves and muscles, especially the heart. The normal serum potassium level is about 3.5 to 5.0 mEq/L (roughly 3.5–5.0 mmol/L since potassium has an equal valence). Values below this range (hypokalemia) can cause muscle weakness and potentially dangerous heart rhythm changes; values above this range (hyperkalemia) can lead to serious conduction abnormalities and arrhythmias. The other ranges listed are either too low or too high to be considered normal, so 3.5 to 5.0 mEq/L is the correct range.