I'd love to get to the bottom of this, so am open to suggestions. When I boost my mb12 intake using good b12 from a local compounding pharmacy, I get noticeable positive response over the jarrows, either sublingually or via injection. However, I get a constant, strong, dull(ie not like salt or acid) and slightly slightly metallic taste in my mouth a few days after adding in this extra dose. I don't know what causes it and I don't know how to find out. I suspect zinc deficiency but I'm getting normal results on a zinc tally test and blood tests. Any thoughts? Could potassium depletion cause taste issues like this?