Hi. I have been on Lithium for 15 years for BP I. I am also on Seroquel and a couple other meds. I gained 70 pounds in 3 years when I started all these meds.

With Lithium, be careful that you don't start drinking alot of Sugary drinks. Some theories state that the weight gain is because people get so thirsty on Lithium that they start drinking tons of juice (which is real high in calories).
Try and stick with water or diet drinks. That might help.

For me, the benefit of Lithium outweighs the weight gain. It has helped me so much.