Vitamin D supplementation- who takes vitamin D?

Who takes vitamin D?  How much, how often?  Why?  How do you measure your blood levels of vitamin D?  Does your supplementation change with the seasons?

I take 1,000 mg x 2 daily- I use the LEF blood testing about twice a year to measure- quick and easy- cheap too- my serum blood levels when I last checked were about 35 (whatever the standard measure is)

http://peoplebeatingcancer.org/article/vitamin-d-key-feature-immune-syst...

David Emerson