I take senna once a week for years now to help constipation,drink plenty of water i eat right diet.when constipated i have strong metalic odour from my mouth .but dentist says i have very good oral health,what else could it be from? constipation?

Common sources: Aside from dental/mouth are sinuses and possible reflux. Severe constipation may worsen reflux through increased intraabdominal pressure, not likely by itself to cause a metallic taste. Talk to your doc about your symptoms and keep a log with their timing and circumstances.

Fiber and water: You may take a fiber laxative like Metamucil and drink enough water daily so that your urine is colorless. For the long term you may try to increase your intake of fiber foods. Consult this site for fiber foods. http://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/in-depth/high-fiber-foods/art-20050948 Wish you good health!

Gerd: See a gastroenterologist. Or can be from infected sinuses, which would trigger visit to ENT. Metallic taste usually signifies bleeding. If your Dentist feels your gums are healthy, and consultation with a Periodontist is not required, seek medical evaluations.