What is the effect of glucose 0.3 m on red blood cells?

The effect of glucose 0.3 M on red blood cells is that it causes them to crenate, or shrink. This is because the glucose concentration outside the cells is higher than the glucose concentration inside the cells, so water moves out of the cells by osmosis. As the cells lose water, they shrink and become crenated.

Crenation can damage red blood cells and make them less able to carry oxygen. In severe cases, crenation can lead to hemolysis, or the rupture of red blood cells.