1200 mg made me narcoleptic. I was was teaching groups of kids at work while slurring words and stumbling around fighting sleep attacks. I would very briefly fall asleep while while I was walking around, teaching, or even driving. I would randomly have sleep attacks where I literally could not resist falling asleep and taking a nap for a while. I had a hour long drive to work and would swerve all over the road because I kept falling asleep. Once I crashed my car on the highway, I stopped driving and had to have someone drive me everywhere until I sorted everything out. My doctor reduced my lithium to 600 mg and said that if the sleep attacks didn't stop I had to be tested for narcolepsy. Luckily the sleep attacks did stop and I was able to work and drive and everything.

My most recent blood test shows that my lithium levels are not in the therapeutic range. I increased to 900 mg and it seems to be a good dose for me.

Good luck sorting out your lithium levels.