What potassium level defines hypokalemia?

• A. <4.0
• B. <3.0
• C. <3.5
• D. <2.5

Answer: (C)

Potassium below 3.5 mEq/L is considered hypokalemia. The normal serum potassium range is about 3.5 to 5.0 mEq/L, so dropping below 3.5 means you’ve fallen out of the normal, with potential effects on muscle and nerve function, including the heart. Clinically, you’ll often see a grading of how low it is: mild hypokalemia is roughly 3.0 to 3.4, moderate 2.5 to 2.9, and severe below 2.5. The defining cutoff for the condition is the 3.5 mark, which is why this threshold is used rather than higher figures.