Does taking lithium make you have a "flat" personality?

Lothium doesn't. Most people are prescribed lithium to try and level out moderate to severe mood swings so they don't experience the depressed and/or hypomanic/manic eisodes. If you consider the symptoms seen in these cycles (e.g., more talkative, more social, mpre energu, etc.), then you could argie thatlithium does. However, the answer is no. It does not flatten one's personality.