Anybody know if D levels have anything to do with it. My level had been 27, got put on 2000iu/day. Had it tested again (in September after a summer with no sunscreen) and it was 48, but doctor said to take 5000iu/day because we were heading into fall/winter. Just had it taken, and it's 36, so now he's got me on 10,000iu/day. Why can't my body keep the vitamin D?