Would they cover it if you did have symptoms? If so, here are some vague symptoms to "have" for your doctor: difficulty thinking clearly, bone pain, unexplained fatigue.
In my experience, no. When I was first tested for Vit-D deficiency the test was not covered, period. I had every symptom in the book (largely because I was extremely Vit-D deficient). My insurance even went so far as to relabel it as emergency bloodwork and tried to charge/fine upwards of $3,000 for it. The doctor's office then retracted the claim and just ate the cost, so I ended up paying nothing. The whole affair was absurd.