I too was started on litium recently and was concerned like you.He has got me on 450mg a day.I will be increased again this week.
I have been really struggling with my depression for over a year.Im not feeling anything from the drug other than I think it helps me control some self harm.
There is a history of bipolar in my family so I think I was put on lithium until I see a pdoc.
Good luck ,feel free to PM