What type of salt solution should be used to lyse red blood cells?

A hypotonic solution is used to lyse red blood cells because it has a lower concentration of solutes compared to the inside of the cells. When red blood cells are placed in a hypotonic environment, water moves into the cells via osmosis in an attempt to equalize solute concentrations on both sides of the cell membrane. As water continues to flow in, the pressure inside the cells increases, which eventually causes them to swell and burst, leading to cell lysis.

In contrast, an isotonic solution would have an equal concentration of solutes both inside and outside the cells, leading to no net movement of water and thus no lysis. A hypertonic solution has a higher concentration of solutes outside the cells, causing water to move out of the cells and leading to cell shrinkage rather than lysis. While saline solutions can be either isotonic, hypertonic, or hypotonic, only a hypotonic saline solution specifically induces the lysis of red blood cells.