What is the normal range for serum sodium?

What is the normal range for serum sodium?

• A. 130-135
• B. 135-145
• C. 145-155
• D. 120-130

Answer: (B)

Normal serum sodium is about 135 to 145 mEq/L. Sodium is the main extracellular cation and helps regulate extracellular fluid balance and osmolality, which in turn supports nerve and muscle function. When sodium is below 135, it’s hyponatremia and can cause cells to swell, especially in the brain. When it’s above 145, it’s hypernatremia and can cause cells to shrink due to dried-out intracellular fluid. The typical reference range labs use centers around 140, with 135–145 as the standard range. The other ranges given fall outside this normal span, signaling abnormal sodium levels.

Normal serum sodium is about 135 to 145 mEq/L. Sodium is the main extracellular cation and helps regulate extracellular fluid balance and osmolality, which in turn supports nerve and muscle function. When sodium is below 135, it’s hyponatremia and can cause cells to swell, especially in the brain. When it’s above 145, it’s hypernatremia and can cause cells to shrink due to dried-out intracellular fluid. The typical reference range labs use centers around 140, with 135–145 as the standard range. The other ranges given fall outside this normal span, signaling abnormal sodium levels.