This medicine should be taken on an empty stomach.
Tips
mistakes
Fourth tone on 空 is the reading that means free or unfilled, and it gives this word, said of a stomach with nothing in it. With first tone, 空心 is a different word meaning hollow.
register
Slightly old-fashioned, and mostly heard around medicine and doctor's orders. The word you will see on modern labels and hospital forms is 空腹, which means the same thing and is read with a first tone.
