My vitamin d 25 hydroxy is low at a 27.8. how do i know which vit d should i take? can i take a vitamin d3 1, 000 pill to help raise it?

Vitamin D: Although there is some controversy about the cutoff of normal level of vitamin d, it is generally agreed that above 30 is a normal level. So, your level is only slightly below that, and 400-500 iu of vit d3 supplement should be sufficient, and 1000 iu will certainly raise it above 30. Depending on your risk for osteoporosis, higher levels of vit d may be recommended.