How can I remove a mirror from the bathroom wall?

Cover the mirror with heavy-duty packing tape as a precaution against the glass cracking or shattering. Insert wooden shims in any gaps between the mirror and the wall. Tap them snug, but avoid forcing them beneath the glass. With another shim beneath your pry bar to protect the wall, gently begin working the bar behind the glass. Maintain a steady pressure and listen for the drywall paper tearing loose from the wall. Gently work along the top and sides of the mirror, releasing a little bit at a time. As you near the bottom of the mirror, support it at the top to prevent the whole thing from popping free of the wall and falling. Once loose, carefully carry it away from the bathroom. If you plan to reuse the mirror, protect it from accidental damage.

Wear goggle and heavy leather gloves.

A mirror adhesive is often used, (I think it is called Mirror Mastic Adhesive.) it is VERY adhesive and difficult to get off the wall -- I have ripped sheet rock trying to scrape it off. So, be prepared to have some difficulties. In removing such a mirror I taped all over the mirror-- up, down, sideways, angles -- then placed a towel over the mirror and tap with a hammer (safety glasses are highly recommended for this.) I used a small towel and slowly did small sections at a time. Use a wide blade scraper (I used an old kitchen/ pancake flipper!) to pull the mirror away fro the wall -- as it comes off in pieces you can carefully cut or tear the tape to remove small sections at a time. When you get to the areas where the mastic is heavily applied -- you may need a stronger scraper. It is a tedious task, but not hard to do. If you so desire, you can save the pieces of broken mirror for another DIY project!! Good Luck!

the drywall or plaster behind it will get ripped then need repaired

Kathy's directions are spot on!