Did finger-prick blood Vit D test - result 41 (normal over 50). GP did test years back - result 19 - but then went up to IIRC 54. Would like mine over 100 because so important. Problem is for years haven't tolerated supplement - some allergic to filler, others filler okay but vit D itself 1,000iu swells brain unbearably. Don't know why can't metabolize. Can anyone recommend a supplement, what do you take? Many thanks.