The tests are of questionable reliability. That doesn't mean they are necessarily worthless, but I would be skeptical of any results.

I've heard people say that challenge tests are better. This would mean taking a chelator before giving the test. Taking a chelator is potentially dangerous if you still have silver fillings because the chelator could pull mercury out of your fillings, worsening your problem.

Silver fillings are about half mercury. The mercury leaks out of them and into your body 24/7. If you have them and heavy metal toxicity, then you can pretty much assume the fillings are a big reason for it.

I don't know much about your situation, but I highly recommend that you get the fillings out and chelate. It helped me a lot after decades of feeling "mysteriously" sick.

Personally, I think getting rid of all mercury exposure is a good thing. Mercury, even in the tiniest of quantities, is highly toxic to Humans.

I never wasted much time or money on testing. Mercury is too fickle and hard to detect without causing more problems to your body. But, there's more than one way to skin an orange. I opted for a more of an empirical method with 4 key criteria:
1) did I have the symptoms of [insert syndrome/dis-ease] (in this case, mercury)
2) did I have a history of exposure to it
3) do I have any direct laboratory testing that confirms it
4) do I respond to the treatment for it

If I could say yes to 3 out of the 4, then I could reasonably assume I had it as an issue to clear up. With mercury, the only lab testing I did was the hair test which will basically just show you if you have issues mobilizing minerals around your body, which I did. Mercury is the usual suspect for that. I also had yeses for the other points, 1, 2, and 4. So, for me, mercury was an issue and treatment definitely helped.

Also, taking glutathione directly doesn't do anything. It's like trying to get a model ship inside a bottle. Glutathione's activity is inside the cell, but it doesn't cross the cell wall. The only way to get more glutathione in the cells is to take precursors like NAC so your cells take that in and make glutathione from it. Aside from that, taking a lot of antioxidants can help protect from mercury exposure. Once you've eliminated all sources, then you can start chelating.

I was trying to figure out the same thing. I saw an old post were someone suggested Direct labs. The test for Hair toxic elements runs $94.