Which electrolyte imbalance is associated with muscle fatigue and weakness?

Hypokalemia, or low potassium levels in the blood, is directly associated with muscle fatigue and weakness. Potassium plays a crucial role in muscle function and neuromuscular transmission. When potassium levels are insufficient, the excitability of muscle cells diminishes, leading to symptoms such as muscle weakness and fatigue. Additionally, potassium is vital for maintaining the resting membrane potential of cells; when it is low, it can affect muscle contraction and overall muscular strength.

While the other imbalances, such as hyponatremia (low sodium), hyperkalemia (high potassium), and hypocalcemia (low calcium), can also lead to various neuromuscular symptoms, they do not specifically present with the characteristic muscle fatigue and weakness attributed to hypokalemia. Sodium is primarily involved in fluid balance and cellular function, while calcium is critical for muscle contraction and neurotransmitter release, and high potassium levels can also lead to muscle weakness but typically manifest with additional severe symptoms such as cardiac disturbances. Thus, the primary link to muscle fatigue and weakness is accurately identified with hypokalemia.