Hello, Thanks for your query. A bad taste in the mouth can be caused by a variety of conditions including dental or gum problems, dehydration, medication (such as some antibiotics and antihypertensives), a yeast infection in the mouth, an autoimmune condition or a respiratory tract infection. Bad breath and an altered sense of taste can also be caused by certain low-carb diets, which lead to the formation of ketones (chemicals that are released in the breath as the body burns fat). I do hope that you have found something helpful and I will be glad to answer any further query. Take care