Blood work for heavy metals only shows recent exposure and then again, they probably have to look for these metals specifically. My urine tests showed lead levels that are through the roof; however, on the blood work, they look normal.
Best test for determining your body burden of heavy metals is, according to the doctors who treated me here, the post provocation urine test. You're given intreveinous chelation with EDTA DMPS whatnot and then you collect urine for six hours. That gives you a pretty good picture of what is in your body.
I don't know much about hair analysis, but am wondering if it is as precise and accurate as the urine analysis which evaluates 21 different metals.
I had uranium! And arsenic! And mostly, lead levels like there's not tomorrow. Mercury not so bad though. So sometimes, you might get a surprise.