I'm sorry you feel as if your depression is returning. It probably wouldn't hurt to take B vitamins, but I'd recommend a B multiple, rather than just B12. The B vitamins work together. Fatigue can be a symptom of depression. If you are getting depressed the fatigue might just be a harbinger. I feel that way when my depression is returning, and then I start "self-medicating" with vitamins and supplements. The real answer is usually a medication adjustment. Sometimes when my effexor starts to poop out, I use l-tyrosine and it seems to help. I don't know what you're taking, but there may be supplements that could help