I have a metallic taste in my mouth when swallowing, particularly when having nothing to eat for a while. what could this be?

Exam needed.: There could be many things that can cause a metallic taste. Have you seen a dentist recently? Bleeding gums can cuse this. So can vitamin deficiencies, hormonal or metabolic diseases and infections. Have a dental exam and then see your primary care for exam and blood work.

Metallic taste: Usually means bleeding. How long has it been since your last dental examination/cleaning. Gum disease is readily treatable in early stages, very expensive as infection spreads. If gums healthy next step is your GP to check for GERD, blood dycrasias, neurological disorders.