The problem with testing urine for mercury is that you are actually testing your inhability to eliminate the heavy metals.
I did this test AND a blood test.
Although my blood showed above the level toxicity in heavy metal, my urine showed very normal presence of metal. My doctor basically said no chelation. But he was speechless when I asked where the mercury was going if it was in my blood and NOT coming out in my urine (getting stored is the anwer I came up with on my own, in my bones, my tissues and in m y hair) THis is why I beleive the hair analysis to be more accurate. Well, in my case it gave me a reading while the urine test said I was okay!