If you are feeling flat when you see your pdoc next let them know. Your level may be too high. I never had trouble with that but I know it is possible (and my levels were kept low after my first toxicity and I really don't remember before that. Actually I do but I blamed feeling flat on high-dose Depakote, not lithium.) Getting the right level that feels good and works can take some time and trial and error. I had different responses to the different releases (lithium carbonate-immediate release; lithobid-extended release and eskalith-continuous release) and so playing with that might help too. I liked eskalith best although I think it's the least commonly prescribed.