Is it considered poor etiquette?

[Sir Joey the 4th]

to go to the bathroom while speaking on the phone

[kiwi]

As long as it's not a camera phone, I'd think it was okay. Who'd know? Don't flush loudly, tho.

[Peachy Keen, Jelly Bean]

If I'm on the phone with someone I talk to all the time or know well (such as my mom or my boyfriend), not only will I go to the bathroom, but I'll let them know that's what I'm doing! However, they do the same when they're on the phone with me, so I consider that acceptable. Now, if it's a professional call or if it's a public restroom, I try to refrain from talking on the phone.

[kittenkatt79]

Well, it can be confusing in a public restroom if you're using the stall. I've been in a public restroom when someone in the stall next to me starts saying, "Hi, how are you?" and I answer back like an idiot only to later find out that she was talking to someone on the phone.

So if you want to avoid situations like that, I'd recommend not using your phone in public restrooms. Otherwise, I use my phone all the time when I'm at home and using the bathroom - I try to muffle the flushing noise though.