Specialties

How long do you have to work in a specialty to consider yourself specialized? People say I'm an emergency nurse, I'm a cardio nurse, etc. Does that mean they have worked in that specialty for a certain amount of time? Just wondering.
It's a matter of self-identification. There aren't any hard rules about it. However, no one can ever say that they are "certified" or "board certified" in a specialty unless they actually have the credential. This is an absolute no-no. Those of us who have achieved that "RN-BC" have worked hard for it and are justifiably very proud of the accomplishment.