There are several different causes of bad breath, and some of them do require medical evaluation and treatment.
By far the most common cause of bad breath is tooth decay or poor dental hygiene. If you have not had a recent dental cleaning
or visit, I would start by doing that. Your dentist
will be able to remove any accumulated plaque or other debris which might be a source of odor; as well, they will be able to determine if there are any teeth that have cavities that might need to be filled.
If your dental visit checks out with no identified source for the bad breath, then it is worth seeing your primary care doctor
to consider other potential causes. One of the most common causes of bad breath is acid reflux disease, or heartburn. This can be controlled with medications and with dietary modifications to reduce the severity of the acid reflux.
Another major cause of bad breath is nasal allergies or sinus congestion. If you have cough, stuffy nose, or similar symptoms, this is a likely cause. Your doctor can confirm the diagnosis and can also help you come up with a medication treatment plan.