What is the normal serum potassium level?

What is the normal serum potassium level?

• A. 3.0-4.0
• B. 3.5-5.0
• C. 4.0-6.0
• D. 5.0-5.5

Answer: (B)

Potassium in the bloodstream is normally kept within a narrow window because it is essential for nerve signaling and heart muscle function. The standard reference range for serum potassium is about 3.5 to 5.0 mEq/L. Values below 3.5 can cause weakness and dangerous heart rhythm problems (hypokalemia), while values above 5.0 increase the risk of hyperkalemia and cardiac conduction issues. The range 3.5-5.0 mEq/L matches the typical reference interval, making it the correct choice. The other options either go too low or too high and don’t align with common lab standards.