Where is sodium stored in the human body?

Sodium is not stored in one single organ; most of it is in extracellular fluid, where it helps control fluid balance, nerve signaling, and muscle function. A significant amount is also bound in bone, which can serve as a reservoir. In healthy adults, total body sodium is usually around 90 to 100 grams, though the exact amount varies with diet and health. The kidneys regulate sodium levels very tightly, reabsorbing or excreting it as needed. This balance is essential because even small shifts in sodium concentration can affect blood pressure and cell function.