Yes, weight gain is a common side effect of gabapentin.

Keep in mind that learning new things, that you didn't know about concerning your medications is going to be difficult to
come to grips with.

Some people respond with disbelief, surprise, shock, and/or horror. So read a bit every day and let it settle in so you will be
able to decide where to go and what to do with the new information.
Our subforum here has many informational posts, and our B12 post is here:
http://neurotalk.psychcentral.com/thread85103.html

I've been collecting medical information on PN for over a decade. I only post here that which is important, and substantiated. On the B12 thread is a link to American Association of Family Physicians, about managing B12 deficiency in patients (the article is written for DOCTORS but is understandable to the layman as well). It was posted by AAFP in 2003, and still today, we see people coming here with horribly low levels, that their doctors have said were "normal". Unless people take that extra step and look into the test results themselves, they would continue to decline and worsen. It is sad but true unfortunately. Replenishing the B12 is simple, and for pennies a day one of the most affordable medical interventions out there today!

The same happens with Vit D. Doctors will test for it, but then turn around and prescribe a decades old version of D(ergocalciferol D2) in a capsule, that we know today, does not work. But the doctors do it anyway, because their reference books have not be updated either.

So as patients we do have to do some homework in this area. Thankfully we have venues like this to discuss things and share information found.