What can cause metallic taste in mouth, blurred vision, bad headache, and teeth grinding

I couldn't say. Have you got to a doctor to get checked out? I did a quick Google, less than 5 min, and got drug interactions, trauma, poisoning, cancer (Bloody WebMD), and a host of other problems. I would really go to a doctor to get checked out.

Kidney failure is also an option. You need blood work as it can take years for signs that your kidneys are failing. Metallic taste h/a, etc sign of urea building up. Don't be afraid to go to the Dr. You may just be Overdoing it on types of vitamins also.