Hyponatremia is defined as a serum sodium less than which value?

• A. 130 mmol/L
• B. 120 mmol/L
• C. 140 mmol/L
• D. 150 mmol/L

Answer: (A)

Hyponatremia means the serum sodium level is lower than the normal body range. The typical normal range is about 135 to 145 mEq/L. So when the sodium falls below 135, it’s considered hyponatremia. Clinically you’ll see it described as mild (roughly 130–134), moderate (125–129), or severe (<125).

In the options given, 130 is below 135, which fits the idea of hyponatremia, specifically the mild range. Values like 140 or 150 are within or above the normal range, while 120 would indicate more significant hyponatremia. The key point to remember is the 135 threshold for defining hyponatremia, with 130 representing a mild category on the common scale.