I think for you. obviously when you start chelating, it kick starts the movement of mercury and clouds your mind up somehow, but then as it continues it clears again, so it might be better if you do go for longer rounds to give your system a chance to get through the brain fog and have a longer round of getting on with the chelating and hopefully getting more mercury out of you.

It's up to you though, you will be the best judge of what you can handle. If the brain fog is simply annoying, I'd stick with the 12 mg, but if you are finding it distressing, then yeah go down to half and see what happens.

more and more people are actually using 6 mg of DMSA because even 12.5 mg can be too much for some, so it will probably still be chelating mercury.

DMSA doesn't directly chelate out minerals, I think the stress of it is the problem and that's why we're supposed to take more antioxidants etc. Problem is, many mercury toxic people are very sensitive to supplements, so it's difficult to find thigns you can take without getting reactions.