Bluesfan,

Steroids effect MANY tests. I don't know how it may effect B-12 (MrsD would know,if it does or does not), but I know for sure that steroids increase glucose levels...especially if you have taken them for a while (even low doses). There is actually a condition called steroid induce diabetes.

They can also effect any autoimmune testing, since they effect the immune system (suppress it).

But one of the other common causes of neuropathy is inflammation (from trauma, toxins, and a vast array of other medical conditions) and steroids reduce inflammation. So testing while taking the steroids will mask the inflammation and hinder any ability to find that inflammation and then treat accordingly.

So, taking a low dose of steroids can very likely skew your testing for PN. It is always best taper off and be off for several weeks (if not longer), but of course this is not always possible. So the doctor has to keep this in mind during diagnostic testing...but it will make his (hard job) even harder.