I have recently been tested for high heavy metals especially arsenic with a "provoked urine test" My doc gave me a chelator and that pulls the metals out of your tissues so they can tell how much of an issue it is. In my case, almost ALL my tests showed I was a healthy person except I felt horrible- fatigue, muscle weakness, numbness and tingling, food sensitivities, anxiety, brain fog and muscle aches to name a few. It wasn't until we got the results back from the provoked urinalysis did we get some answers. Turns out the heavy metals in my system are related to a methylation pathways isssue I'm having, causing heavy metals to build up in my system. I was really surprised to see how high arsenic got, but I eat a LOT of brown rice and seafood and there might be a few other sources as well. If you eat a lot of chicken, or drink wine, AND have a methylation issue, this can cause high arsenic. My doctor is an integrative doc so the provoked urine test may not be a common test people give. My blood arsenic and mercury were "in range". But when both my doc and chiropractor saw the tissue load results, they immediately recommened chelation. Oh, and heavy metals are an issue in themselves, but also supress the immune system. I have chronic lyme and my doc says the heavy metals in my tissues are the main reason I'm not healing no matter what I try to take. Hope this helps!