I have tiled bathroom walls and now have decided to do around top of shower. This is already drywalled do I need to take down and use different backerboard?

What u gave is a vague description of your situation.

Do u have tile in shower area and wanting to continue it to ceiling?

Wet areas should be done with concrete board. If s/r is in good condition and above shower head u should be fine.

Chuck

If it's at least 6' above the drain the sheetrock is fine. Clean it well with TSP before applying the thinset.