I'm reading everything you guys are posting on this. My dd is 12 next week(80 lbs.)and has a good diet which consists of homemade cultured vegetables, seaweed, celtic Seasalt , celiac diet, yogurt, homegrown organic foods. RO and distilled water, no sodas. I do have the swanson selenium you are mentioning. I've never given her an individual selenium tablet. Few times a week, I give her one vertical drop of Lugol's in water, and she does brush her teeth with one drop about once per/every 2 wks. I do give her 125mg. of potassium and 125 of magnesium, 1g. vitamin C, D3. How many mg. of this particular selenium do you give a 12 year old? Thanks, HH. Her ADHD is through the roof lately for some reason.