The preferred option for pilots is to come in on a day off if it's not a serious complaint made against you. If HR are involved they will make it an IV because they know people are watching, even if it's only HR who are on side. But don't worry it won't affect your roster because they make sure they pick the right DAY OFF to convert to an IV.
If they ask you to come in on a day off, tell them you're only available on Friday. If they take you off a flight for an IV then you probably have bigger things to worry about.