I too have a low D-3 level but it is coming up. My pcp has me on 10, 000 cc a day which is still way in the safe zone. I don't know how many different ways levels are mesured but according to lab my doc uses the green zone (good zone) is 40 to 100. I just in green at 41.
My doctor said to take D-3 with the meal that has the most fat as D-3 is fat soluable.
The brand I take is from Metagenics lab mine is 5000 cc per capsule. Their products are made to very strict guidelines and can only be bought at a D octors, dentidt or soke chiroractors offices.