There is a sudden bitter taste in my mouth, what's causing it?

Symptom not disease: Whether dietary, due to drugs or a physical condition, a metal taste is a the main reason for a metal taste is something in your system that is reacting with your body chemistry to produce a metal taste. A metallic taste in the mouth, or dysgeusia, is a common side effect of a wide variety of medical treatments and medications, and is sometimes a symptom of a medical condition.

Gerd,from gums,meds: Sudden bitter taste can be from gum disease or esophageal reflux disease.It can also be result of some meds or over the counter supplements or antibiotics if it persist check with your doctor and dentist.