I am not diabetic but i sometimes get a metallic taste in my mouth as well. this usually happens when i have been handling aluminum foil or i have been pulling staples at the uphostery shop that i work in. I can also get it from some kinds of stainless steel. especially in spoons. it sounds stupid, i know, but it does happen.
Do you take oral medication for your diabetes, and if so what kind? Some of the medicines will give you the metalic taste. I take Metformin, also known as Glucophage, and it gives me the metalic taste sometimes.