Check your level !
I measure a level on every patient that comes in for a consultation in illinois as 99% of the people i see are low.
A study in hawaii showed 50% are low! i personally take 7, 000 iu daily with vit k to keep my level at about 80 (normal range 30-100), and studies showing benefit for most conditions are in levels above 50. Guestimate dose is 30iu per pound, then follow levels and adjust accordingly.