[SilasX]

But then why do they use saline instead of (relatively) pure water in IV bags? I would think it's fair to say there's some sweet spot when the goal is hydrating the body, though I doubt it's what the slimy advertiser above was intending to convey.

[dahfizz]

They use saline because it goes directly into your blood stream. If they used pure water, the osmotic pressure would force water into your cells, causing them to burst (hypotonic).

You can drink pure water because it "becomes" saline as it mixes with the food in your stomach.

Even unfiltered tap water doesn't have very many ions compared to blood or saline solution. Most of your ions come from your food.

[NovemberWhiskey]

They use saline instead of pure water because it's isotonic with respect to serum/plasma. i.e. you're not going to go into electrolyte imbalance if a lot of it is put into your blood.

Normal saline is about one-quarter the concentration of sea water, by the way.

[Bloating]

here I thought I was saving cash by injecting sea water