I have been trying to get my low vitamin D levels up to normal for a few years now, so I have done some reading on it. I mostly just get more confused about what to do. I have learned, though, that the form of vitamin D we get from sunlight and from food and supplements has to be converted, first by the liver and then by the kidneys, into the form that's usable by the body. Enzymes are involved.

That leaves a lot of places for things to go wrong.

from Wikipedia: Vitamin D refers to a group of fat-soluble secosteroids responsible for enhancing intestinal absorption of calcium, iron, magnesium, phosphate and zinc.

I read things that say that vitamin D supplements must be taken with magnesium, must include vitamin K - it's just very confusing!

I have tried supplements to get my levels up to normal, because low levels are associated with depression and autoimmune problems, but my level doesn't go up much. I'm not sure that my depression or autoimmune problems would improve if I did get my vitamin D levels up to normal. As far as I know, the autoimmune problems may be causing the low vitamin D level.