When they test for mercury, make sure they test a hair sample rather than blood. mercury does not stay in the blood stream. Instead, it settles in your organs. A blood test will only reveal RECENT exposure to mercury. A hair test is much more accurate. However, make sure the person who performs the test truly understands the results. The mercury number may seem small to someone used to doing blood tests. They need to compare the number to the levels of other metals that belong in the blood. This will tell them if the levels are too high. I am not a medical expert, but this is what my son's doctor told me. There are medical sites on the web that also support this technique.
Also, testing for lead is always a good idea. Even if you live in a newer home, your child could have been exposed.
Hope the info helps. ↑