Testing for bad breath requires a standardized examination, including physical examination and laboratory tests. 1. Physical examination: the doctor will smell the patient’s mouth for odor and observe whether there are ulcers and erosion of the oral mucosa; also observe whether there are abnormalities in the teeth. Physical examination can initially determine whether there is bad breath or not, and can also help to diagnose the causes of bad breath. 2. Laboratory examination: laboratory examination mainly includes saliva examination and breath examination; saliva examination mainly adopts high-pressure liquid chromatography analysis; breath examination mainly adopts gas chromatography and sulfide monitor. Laboratory tests can help diagnose the causes of bad breath. If you suspect that you have bad breath, you can go to the stomatology department to actively clarify the cause of the disease and avoid delays.