You mean 500mcg (micrograms)?
Even so, that is not a normal amount, that is a BIG dose. The requirement is 4-6mcg a day, and my multivitamin has 5mcg. In other words, 500mcg is a megadose and no less.
It probably doesn't matter, though. I actually started taking 500mcg sublingual pills a couple of days ago despite a high-ish (but not out of the range) level.