you can say something like すこし良くなりましたか?(are you feeling little better) also お大事に（get well soon）：this is a phrase used to someone who is still ill and recovering from.

You can translate these phrases like this; "Are you OK ?" → "だいじょうぶ(大丈夫)ですか？", "How is your condition ?" → "たいちょう(体調)はどうですか？" If you want to say more casual, you can use "だいじょうぶ？" and "たいちょうはどう？"