350 is borderline low. Anything below 400 should be either further evaluated with an MMA test, or you can start methylcobalamin (methylB12) orally) now yourself.

Low D is being found in about 1/2 the US population, and is linked to many medical problems. Many people on these boards have tested low or very low:

Please read this thread and watch both videos:
http://neurotalk.psychcentral.com/thread92116.html

There is preliminary evidence of low Vit D and diabetic neuropathy as well.

I would stop the Claritin for two reasons. 1) it is really a very poor antihistamine, and 2) it can affect the liver (which it did to me). Better would be Zyrtec, and if that makes you tired, break them in half, like I do. They work just as well at 1/2 or 5mg, which most people and doctors don't know.

Allergies also respond to antioxidants, like grapeseed extract, which will also help the PN. 300mg a day minimum. Some people can reduce or stop antihistamines when using this natural antioxidant.