drug abuse?

I’m suspicious that my best friend has been abusing lithium. I’ve seen her acting funny but I want to get the facts about it before I accuse her. I’ve tried looking around online but am not finding what I would like to know about it. How do you abuse lithium? and how much do you have to take to mess you up? I know she is perscribed it and I don’t want to accuse her if she’s just taking how she’s suposed to but I know nothing about the drug.
any help please?

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