Hi Jinx, as you know the testing for mercury is notoriously inaccurate, which is why it's not wise to try and look for a level as much as look for the hallmarks of mercury (what it causes) and the minerals that have certain pattern of distortion.

The way to do that is usually with the hair analysis test. Again, the levels of mercury may not be telling, but the mineral patterns may be very evident in that mercury is active.

Here is a link you may find helpful
http://home.earthlink.net/~moriam/HOW_TO_hair_test.html#counting_rules

One other sad problem is, some of the sickest patients show the lowest levels of mercury....make sense I guess when you consider they are obviously retaining it deeply, rather than readily excreting it, so the levels maybe high, but could be bound up in brain and body organs/tissue....also can mean the levels "may' be low, but the person may react severely to only a very small amount of mercury.

Many meanings to why and not fair to diagnose a patient based on levels alone, particulary when one considers the nature of mercury itself.

Hope that helps (great pic by the way lol).