When you combine sodium chloride (or salt) with sterile water, you get saline solution. The proportions or concentrations of sodium chloride can vary, but typically, commercially available saline solution contains just 0.9% sodium chloride. This is what is used by hospitals in saline drips or intravenous infusions (IV).
Saline solutions are a common treatment for dehydration, especially for patients who are incapable of any oral intakes of liquids or nutrients. In many cases, the doctors will combine saline solution with dextrose or glucose, which will help minimize the amount of sodium in the blood stream and prevent the corresponding complications.
Saline solution also has many other medical uses. For example, it is used for nasal irrigation (for those who suffer chronic sinus problems), or to clean and store contact lenses. Note, however, that nasal sprays and contact lens products also contain other chemicals for their specific purpose, and cannot be used interchangeably.
While saline solution is readily available and quite affordable, it is possible for people to make their own—but only for the purpose of nasal irrigation. Simply combine half a teaspoon of non-iodized salt with one cup of sterile or purified water (check the labels of bottled water). For any concerns or questions about homemade saline solution, it is best to consult a doctor or pharmacist.
An at-home nasal saline solution can be made by combining ½ teaspoon of non-iodized salt with one cup of purified water and allowing it to reach room temperature covered. A solution prepared at home should never be used for anything other than nasal irrigation. If you are not sure how to safely rinse nasal passages, ask for directions from a doctor or pharmacist.