While most cases of bad breath are caused by poor oral hygiene, tooth decay, or gum disease, other potential causes exist. If you have persistent bad breath despite maintaining good oral hygiene and dental treatments to address oral concerns, it may be time to visit your doctor. Other potential causes of bad breath include sinus infections, postnasal drip, certain medications like antibiotics and antidepressants, and conditions including diabetes, liver disease, and kidney disease. If you are concerned about your persistent bad breath, consult with your doctor to determine the cause and possible treatment options.