Water for injection

Water for injection is water of extra high quality without significant contamination. A sterile version is used for making solutions that will be given by injection. Before such use other substances generally must be added to make the solution more or less isotonic. It can be given by injection into a vein, muscle, or under the skin. A non-sterile version may be used in manufacturing with sterilization occurring later in the production process.

If it is given by injection into a vein without making it more or less isotonic, breakdown of red blood cells may occur. This can than result in kidney problems. Excessive amount may also result in fluid overload. Water for injection is generally made by distillation or reverse osmosis. It should contain less than a mg of elements other than water per 100 ml. Versions with agents that stop bacterial growth are also available.

It is on the World Health Organization's List of Essential Medicines, the most effective and safe medicines needed in a health system. Water for injection is available over the counter. The wholesale cost in the developing world is about 0.03 to 0.15 USD per 10 ml vial. In the United Kingdom this amount cost the NHS 0.25 to 1.40 pounds.