When i started lithium I gained 30 lbs in 3-4 months. It made me gain more weight than meds that are supposed to cause more gain, like Depakote or Seroquel. It did level off and probably I was drinking at least some calories as I had to learn to like water when I started lithium (I grew up with a well and had a hard time drinking non-well water). But I did put on weight fast for a bit.