love your name as that's what my dad calls me!!
I have 200ug tabs as well and I take them once every 3-4 days. There's no science in this but my mum was advised to take selenium by a nutritionist for other reasons and was told it is pretty strong stuff. So I'm taking it easy. And as Meg says, Marilyn G says 100ug a day. I think even that's probably quite alot.
I think the jury's still out on Selenium requirements, but generally speaking the info I have is
Life-Stage Men Women Pregnancy Lactation
Ages 19 + 55 mcg 55 mcg
All ages 60 mcg 70 mcg
Results of the Total Diet Study, a national survey conducted by the U.S. Food and Drug Administration (1982-86), indicated that the diets of most adult men and women provide recommended amounts of selenium (10).
I would not personally recommend more than 100mcg per day.