I've tried Lithium in the past and never gained weight and I'm the type of person that if the side effect is to gain weight I always gain weight. I have tried both Lithium Citrate and Lithium Carbonate and had side effects other than weight gain on both. On Lithium Citrate I got really bad hives, while Lithium Carbonate sent me into a hypo-manic episode. I'm on Lamictal too and apart from the really dry skin and fear of rash I really enjoy the way I feel. Good luck with the new meds!