I came across this article that mentioned that high dose thiamine supplementation can help the fatigue associated with IBD and fibromyalgia:
http://www.prohealth.com/library/showarticle.cfm?libid=18187
https://www.prohealth.com/library/high-dose-thiamine-improves-fibromyalgia-symptoms-31178
I tried taking three 500 mg. capsules three times a day for a few weeks but I did not notice an improvement in my levels of fatigue.
I also thought it might not be good to take just an isolated B vitamin by itself, that it might cause a deficiency of other B vitamins.
About this blog
This blog examines current ideas on alternative treatments for Crohn's disease. Although the medical community will tell you that diet doesn't matter, or that alternative treatments are worthless for treating Crohn's disease, this is only because there hasn't been as much double blind clinical testing for most alternative treatments. Therefore they cannot with certainty offer them to you. But, the truth is, many treatments can have an effect on Crohn's disease, or at least improve your general health. We attempt to examine them here.