As cathyhuns says, she should have her thyroid medication level checked by a blood test at least yearly, six months is better. One of the main contributors to the tired feeling has nothing to do with vitamin intake, though. See if you can encourage your mother to become more physically active. Many gyms and ealth clubs have programs for elderly people. Often there is a significant discount as well. I have friends whose parents reported remarkable improvement in, not only energy levels, but mental alertness after just a few sessions...