Hair tests don't show high mercury until you've reached what Dr. Huggins calls "stage 3". At this point, the body can no longer store mercury and blood levels stay high. At this point, mercury will show up on hair and non-challenged blood tests.

Hair tests, however, are useful for detecting mercury before you reach stage 3 if you know what to look for. There are "signatures" that "give-away" the presence of mercury, but of course, you need to know how to interpret these signatures.

Dr. Cutler has an excellent book on this subject called Hair Test Interpretation: Finding Hidden Toxicities.

This book reveals exactly how to read hair tests and find mercury toxicity long before stage 3 hits.