If your blood becomes too concentrated with Iona, what will happen to the red blood cells

The red blood cells would burst and die from the excess of concentration

If the fluid is very concentrated, the cell will lose a lot of water, causing the red blood cell to shrink and die. On the opposite side of things, if the body fluids are too dilute (hypotonic), water will diffuse into the red blood cells (because the inside is more concentrated than the body fluid), causing the cells to burst open.