system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: The science of saline - why can we drink pure water, but when we put water into our bodies in other ways, like an IV, must we add minerals to it?
gpt
Your blood has a salinity concentration of about 0.9%, this is why most IV fluids have a similar “salt” concentration. If you were to hypothetically flood someone with pure water through an IV, it would offset the natural gradient of 0.9% causing fluid to flow into your cells and cause extreme swelling.