I have a multi that has 150mcg(potassium iodide) and I have kelp pills. I haven't been taking the kelp pills, because I didn't know if that would be too much iodine considering my multi already has iodine. The kelp pills have 350mcg of iodine.
Look up TC's article on that very subject.
Just searched it and the article is no longer there.
Heres one of his articles...
I've done a lot of research on this lately. Assuming you don't have any pre-existing thyroid issues, up to 500 mcg would probably be fine. Once you go past that, there seems to be an increase in TSH... an increase in TSH is not a huge deal but it is certainly not optimal, and some researchers even consider the increase as 'subclinical hypothyroidism'. Yes you read that right, there seems to be a fine line between iodine intake, and TOO much can actually be a negative.
A smaller thyroid volume is better than a larger thyroid volume, if I recall correctly. Iodine intake is weird in this regard. More iodine intake in the short-term seems to decrease thyroid volume, while longer-term studies (over months and years) show that those with a lower/more moderate iodine intake actually have smaller thyroid volumes than those with an excessive iodine intake.
Additionally, kelp / bladderwrack is interesting, I recall reading some studies suggesting that it may be good as an anti-estrogenic (reducing 17beta-estradiol levels). I believe this needs more human studies though.
Well for what it's worth when I had a blood test, my TSH was 1.11. That was with taking the multi and some other pills(Zinc, Vit D, Magnesium, Fish Oil) but without the kelp pills. I then had another blood test later on while I was on the kelp pills and my TSH went up to 2.0. They never tested T3, or T4.