The caps I take are 500mg (after malic acid intake).
It's quite a high amount I know, but it evens out with the potassium I get from the Iodine I supplement.
Most of the supplements I take.. their doses are based on how I feel after.
Certan supps, like Mag and VitC/D... Can be had in huge doses with little worry, and mild side effects like diarrhea(mag and c).
Also, I have read certain things about certain supplements, and our current climate.
Magnesium is a big one. Tons of north americans are deficient on it. Usually I can feel when my body wants more too.
Keep pickin my brain if I haven't answered your question(s).