I've been keeping copies of labs for years. Vit D is what I'm looking at right now. Last Nov 2016, my 25 hydroxy came in at 42 on a range of 30-100 and remarks said Optimal.

I don't think that is Optimal for me. This to me is low end of range.

2014 my labs came in at 49, same range. Same comment.

Back in late 2006 when I came up so deficient, 16 as I recall. I worked hard to bring that up and over a year or more got to 80 and remember feeling so good.

Then in 2010, had hip replacement and had read that Vit D levels can drop with surgery and sure enough that 80 became 40. So again working to get that level up and it's being stubborn and I even take the K2 that is said to be for best absorption.

Maybe one of these days soon I'll take 40-50K of D3 and not take any for the rest of the week. Maybe my system needs a boost.

Just my thoughts for me and maybe others need to be aware too. Spend days at the beach and those Vit D numbers will be great.

As always do your research and talk to docs if need be.