In medicine saline is a solution of sodium chloride in water.

Normal saline is the solution of 0.9% w/v of NaCl. It has about the same degree of osmolality as blood, and as therefore used frequently in intravenous drips (IVs) for patients who cannot take fluids orally or have developed dehydration.

Other combinations are frequently used, such as dextrose (glucose) 4% in 0.18% saline. As the molecular weight of dextrose is greater, this has the same osmolality as normal saline but contributes less sodium to the circulation.

The amount of normal saline infused depends largely on the needs of the patient (e.g. ongoing diarrhoea or heart failure) but is typically between 1.5 and 3 litres a day.