What's D problem?

My primary care doctor's office left me a message yesterday to inform me that my most recent blood test showed a vitamin D deficiency.

This could explain my weight loss; one of my sisters lost a frightening amount of weight several years ago, and it turned out to be a vitamin D issue. She's fine now, thank God.

Whether this could account for my missing white cells remains to be seen Monday, when I return to the hematologist for the results of my bone-marrow excavation.