Hypernatremia is defined as which of the following?

Hypernatremia is defined as which of the following?

• A. Blood sodium less than 136 mEq/L.
• B. Blood sodium over 145 mEq/L; deficit of water to salt.
• C. Blood sodium between 136 and 145 mEq/L.
• D. Excess water relative to salt.

Answer: (B)

Hypernatremia happens when there is a relative shortage of water compared with sodium, so the serum sodium rises above the normal range. This most often results from not drinking enough water or losing free water (without adequate replacement), which raises extracellular osmolality and can cause cells to shrink. The best option describes a serum sodium above 145 mEq/L with a deficit of water relative to salt, which captures both the high sodium and the underlying water deficit. The normal sodium range is about 136–145 mEq/L, so values below that indicate hyponatremia, not hypernatremia. Saying there is excess water relative to salt would dilute sodium and also describe hyponatremia, not hypernatremia.

Hypernatremia happens when there is a relative shortage of water compared with sodium, so the serum sodium rises above the normal range. This most often results from not drinking enough water or losing free water (without adequate replacement), which raises extracellular osmolality and can cause cells to shrink. The best option describes a serum sodium above 145 mEq/L with a deficit of water relative to salt, which captures both the high sodium and the underlying water deficit.

The normal sodium range is about 136–145 mEq/L, so values below that indicate hyponatremia, not hypernatremia. Saying there is excess water relative to salt would dilute sodium and also describe hyponatremia, not hypernatremia.