What is the normal serum sodium (Na+) range?

What is the normal serum sodium (Na+) range?

• A. 140–150 mEq/L
• B. 135–145 mEq/L
• C. 120–130 mEq/L
• D. 145–155 mEq/L

Answer: (B)

Sodium level is a key indicator of extracellular fluid balance and osmolality. The normal serum Na+ range is about 135–145 mEq/L. Values within this window support proper fluid distribution and nerve/muscle function. When Na+ falls below 135, it signals hyponatremia, which can cause confusion, seizures, or edema due to fluid shift into cells. When Na+ rises above 145, it signals hypernatremia, which can lead to dehydration and neurologic symptoms from fluid moving out of cells. Among the options, 135–145 mEq/L stays entirely within the normal range, while the other ranges extend into hyponatremia or hypernatremia zones.

Sodium level is a key indicator of extracellular fluid balance and osmolality. The normal serum Na+ range is about 135–145 mEq/L. Values within this window support proper fluid distribution and nerve/muscle function. When Na+ falls below 135, it signals hyponatremia, which can cause confusion, seizures, or edema due to fluid shift into cells. When Na+ rises above 145, it signals hypernatremia, which can lead to dehydration and neurologic symptoms from fluid moving out of cells.

Among the options, 135–145 mEq/L stays entirely within the normal range, while the other ranges extend into hyponatremia or hypernatremia zones.