How does shielding at max HP affect Max HP damage?

Question

If you shield yourself while at full HP, your HP bar increases to make space for the gray shield HP. If you get hit by any %HP damage while the shield is up, will it take the shield HP into account when calculating damage?

Also, say you use a shield while missing any amount of HP, will % missing/current HP damage take into account only your champion's HP or that plus the shield HP as well?

Answer 1

Shields have no effect on the calculation of Max HP, Current HP, or Missing HP damage. The amount of damage will be calculated only considering your actual HP. After calculation, when the damage is applied, it will first be absorbed by your shield(s) before any residual damage affects your actual health.

This is in contrast to Bonus Health. (For more info on that, see this question.)