Hello, Since you are having old blood and metallic taste in the back of the throat you should avoid taking very rich food, prefer taking boiled food over oily spicy food for a couple of days. Poor dental hygiene, indigestion, gastritis, heartburn can cause such symptoms. Take antacids and PPIs for relief. Avoid constipation. Take laxatives at bed time. Take small quantities of food multiple times a day. Other medical conditions that can cause metallic taste in mouth are sinusitis, ear infections, RTI and injury or trauma to the head that causes damage to the central nervous system. Radiation therapy to the head and neck also causes such symptoms. You can maintain your oral hygiene. Rinse your mouth & gargle with warm salt water 2-3 times a day. Take steam inhalation. Rinse your nasal passage with saline solution carefully. Get clinically examined by an ENT and get treated at the earliest. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Nupur K., General & Family Physician