In medicine saline is a solution of sodium chloride in sterile water. Sodium chloride (NaCl) is ordinary salt. Saline solutions are available in various concentrations for different purposes.
Normal saline is the solution of 0.9% w/v of NaCl. It contains 154 mEq/L of Na+ and Cl−. It has a slightly higher degree of osmolality compared to blood (hence, though it is referred to as being isotonic with blood in clinical contexts, this is a technical inaccuracy), about 300 mOsm/L. Normal saline (NS) is therefore used frequently in intravenous drips (IVs) for patients who cannot take fluids orally and have developed severe dehydration. Normal saline is typically the first fluid used when dehydration is severe enough to threaten the adequacy of blood circulation and is the safest fluid to give quickly in large volumes.