The Chao Doctor will examine your Chao. The Chao Doctor will tell you some strengths/weaknesses of your Chao and will explain how it is feeling. An important thing about the Chao Doctor is that he will heal your Chao if it is not feeling well! If your Chao is coughing or groaning, it could mean that it is ill or has a stomach ache. Therefore you should take it to the Chao Doctor and he will give your Chao a pill to take, making it feel much better!
A dangerous glitch exists on the Dreamcast version of the game. Taking your Chao to the Chao Doctor after it has reincarnated can result in the game freezing/data being deleted. See the Chao Death section.
Below are all the illnesses your Chao can get, and medicine that the Chao Doctor will give it to recover.