to ask you to diagnose my rash??

[bruffian]

It's totally flat. Sometimes it is very pale (skin coloured, if you peer hard it is slightly scaly). Sometimes it goes reddish pink. It doesn't itch or bother me in any way. It looks like a splash mark up my arm.

YABU. Go to your GP.

Seems like such a waste of her time!

Go to the gp if your worried

How long have you had it for? If it has only been a few days maybe wait a while as it may just return whence it came. Or, if you don't want to waste the GPs time, maybe show it to a pharmacist first?