Hyponatremia refers to alower-than-normallevel of sodium in the blood. Sodium is essentialfor many bodyfunctions including the maintenance of fluid balance,regulation ofblood pressure, and normal function of the nervoussystem.Hyponatremia has sometimes been referred to as"waterintoxication," especially when it is due to the consumptionofexcess water, for example during strenuous exercise,withoutadequate replacement of sodium.
Sodium is the major positively charged ion (cation) in thefluidoutside of cells of the body. The chemical notation for sodiumisNa. When combined with chloride (Cl), the resulting substanceistable salt (NaCl).
The normal blood sodium level is 135 - 145milliEquivalents/liter(mEq/L), or in international units, 135 - 145millimoles/liter(mmol/L). Results may vary slightly amongdifferentlaboratories.