Which value is outside the normal reference range for adult serum sodium?

Which value is outside the normal reference range for adult serum sodium?

• A. 138 mEq/L
• B. 140 mEq/L
• C. 145 mEq/L
• D. 146 mEq/L

Answer: (D)

Serum sodium is kept in a narrow range to maintain extracellular fluid balance, typically about 135–145 mEq/L. Values of 138, 140, and 145 fall within this range. A value of 146 mEq/L is outside the normal range, indicating hypernatremia. Hypernatremia usually results from relatively more water loss (dehydration) or too much sodium relative to water and can affect cellular function, especially in the brain, so it warrants attention.

Serum sodium is kept in a narrow range to maintain extracellular fluid balance, typically about 135–145 mEq/L. Values of 138, 140, and 145 fall within this range. A value of 146 mEq/L is outside the normal range, indicating hypernatremia. Hypernatremia usually results from relatively more water loss (dehydration) or too much sodium relative to water and can affect cellular function, especially in the brain, so it warrants attention.