[nocrapman]

Most common cause of low vitamin D in the US is living in the north east!
The less the sunlight - more severe the def.
I test most my pts'  (in Central/northern NY) vitamin D and 70% show up deficient (including myself).

[Folsom]

Yes but some people are outside a lot, or supplement a lot, but don't produce high numbers.

In that case, seriously, it's liver related so often.

Vitamin D is actually a hormone, and it's fat soluble... If you know what the liver does, well, there you go.

[Kenneth Patchen]

Kenneth, low D can also be partial to poor fat processing, particularity the liver.

That doesn't seem to be the case for me, my liver is fine. It's due to the overcast skies which can be so oppressive in northern NY as to be unbearable. Happily I'm now able to return to the land of cotton several times a year for the sun, as I'm doing now.

Interestingly, northern doctors are now talkng to, and testing, patients about/for vitamins, especially D and B. When I talked to my doctor twenty years ago, he said to eat right and not to be too concerned. Now, he's concerned.

Cheerio,
KP

[SteveFord]

I had blood work done prior to sinus surgery, nothing seemed out of whack.
The differences between men and women's vitamins appears to be mostly iron and calcium levels.
I love dairy products so maybe that's what has been screwing me up. 
That and old age creeping up on me.