EDTA will only take Hg out of your blood system if it's there, so it will only chelate if you are currntly being exposed to Hg or have been exposed within the last 48 hours. It's generally understood in the comparison studies that it chelates virtually no Hg. However, Calcium EDTA (The none Yellow EDTA) if dripped in after an IV of DMPS will greatly increase excretion of Hg. I did this towards the end of my 2.5 year chelation.