What is the normal range for the extracellular concentration of sodium?

The normal range for the extracellular concentration of sodium is approximately 136 to 145 millimolar. This range is crucial for various physiological functions, including maintaining fluid balance, nerve transmission, and muscle contraction. Sodium plays a vital role in regulating osmotic pressure and hydration in the body.

The choice of 136 to 151 millimolar may include the upper limit of normal, as some references can extend slightly beyond the classic range of 136 to 145 millimolar but still generally recognizes 145 millimolar as the upper threshold for physiological normality. Therefore, while it might be a slightly broader range, it aligns with physiological considerations.

Understanding this concentration is important for analyzing conditions like hyponatremia or hypernatremia, both of which have significant health implications. The options that suggest lower or considerably higher ranges do not reflect the accepted normal physiological concentrations of sodium in extracellular fluid.