So I've been wondering around, thinking about if it would be wrong to use the character か after the shortened phrase 元気。That is 元気 as in [ お元気ですか？]. Would it still mean the same if you did it like this [元気か] or would that be grammatically incorrect? The point is to make certain to the person talking to that it is a question and that you are not just saying "fine".
"元気か?" is grammatical, but it tends to sound fairly blunt and/or haughty. In fiction, an old man, a stereotyped strict father or a yakuza boss may say this. Usually "元気?" with a rising intonation is used in friendly and casual conversations.
If such a question is not directly cast to a person, "noun/na-adj + か" may be more acceptable. People often say "マジか?" or "アホか?" when they saw something unbelievable, although these still sound a little rough.