Having a bitter taste in one's mouth is often due to a lack of hydration, or a side effect of taking certain medications. Hydrate yourself, and check your medications for interactions. If it persists you should see your doctor, and perhaps a dentist since there may be an oral hygiene issue that needs to be addressed.
It could be caused by tooth decay, gastroesophageal reflux disease, medication side effect (especially Biaxin), sinus infection, heart burn, or hiatal hernia. Consult your doctor.
There are several reasons for bitter taste in mouth. very often a virus or may be sinus infection or some upper GI problems. It is better consult a physician.
Different conditions can cause a bitter taste in mouth (gastrointestinal problems, intoxication.. ) In your case, I think the causes can be a gastric reflux.
