"On an empty stomach" is a commonly used phrase to describe the act of consuming food or medication without eating beforehand. However, there are various synonyms one can use to convey the same meaning. One can say "before eating anything," "prior to breakfast," "fasting," "without having eaten," or "without food in the stomach." Another option is to use a more descriptive phrase such as "before breaking the fast," "in a state of hunger," or "on an unfilled stomach." Using synonyms for phrases like "on an empty stomach" can help add variety to one's writing or speech and make it more engaging.