How can I restore a bathroom door handle?

How old is the handle? If the handle is rusting then it most likely is not genuine or solid chrome, only chrome coated.

Hi. You could try to sand the rust, and spray it with a metallic paint.

Hi Sharon. I'm Cindy. Begin by taking the handle off the door. This is going to sound crazy, but next step is to put the handle and all of its hardware into a crock pot. Fill the crock pot with enough water to cover everything. Set it on low and wait overnight. Next day unplug the crock pot and remove everything. Rinse everything with clean water. Then use an old toothbrush to clean in all the nooks and crannies. If any rust is still present, sand it with a fine grit sandpaper. Wipe it down and let it all dry. After that, you can paint everything with a paint intended for bathrooms. Put it back together and put back on the door. I hope this helps you. Good luck from Cindy.

rub it really well with steel wool or crumbled up ball of aluminum foil

I had a door handle that got tarnished and looked bad, but it was on my shed door. All I did was cover the door around it with plastic wrap and/ or paper (taped on) making sure it went right up against the knob bottom and sprayed it with Rustoleum paint the color I wanted which was a shiny gold. It is a good idea to remove some rust too if loose.