Normal Saline, or 0.9% saline, is a crystalloid solution used ubiquitously for dehydration and hypovolemia. It is compatible with blood product transfusion and most medications. It is classified as an isotonic fluid, however, the concentration of NaCl is higher than found in humans at 154mEq/L of both Na+ and Cl-. There are concerns about the deleterious effects of solutions with supraphysiologic chloride concentrations. It is typically the first-line fluid used in trauma resuscitations, head injuries, acute neurologic conditions where hyponatremia should be avoided, and the treatment of mild hyponatremia.