Hypokalemia is defined as which of the following?

• A. Blood potassium over 5.1 mEq/L.
• B. Blood pH above 7.45.
• C. Blood potassium less than 3.5 mEq/L; can cause muscle problems and slow GI.
• D. Edema.

Answer: (C)

Hypokalemia is low potassium in the blood. It is defined when serum potassium falls below 3.5 mEq/L. This deficit makes excitable membranes less stable, leading to symptoms such as muscle weakness, cramping, fatigue, and slowed gastrointestinal motility. That’s why the statement describing potassium less than 3.5 mEq/L and noting muscle problems and slowed GI motility is the best choice. The other options point to conditions that aren’t about low potassium: potassium above 5.1 mEq/L signals hyperkalemia, which carries different risks; a pH above 7.45 indicates alkalemia, not a potassium definition; edema reflects fluid balance issues rather than potassium level. Potassium is tightly regulated because it sets the resting membrane potential of cells, especially in nerves and muscles, and shifts between intracellular and extracellular spaces (influenced by factors like insulin, catecholamines, and acid-base status) can alter the measured serum level.