Interesting, I just happen to be going through early intervention of lithium toxicity. However, in my case I had an on the ball psychiatrist.

Your mother's psychiatrist ought to have had her undergo regular blood testing (no more than three months between). He should have been including in those tests, screening of kidney function, calcium levels, and thyroid/parathyroids levels. These tests should be graphed in such a way as to show how these results are trending.

In my case, my psychiatrist saw my kidney function as trending down and concerning trends regarding my calcium and para/thyroid hormone levels. I was immediately referred to specialists for screening. Thank goodness my kidneys checked out fine but my medication treatment will be changed anyway. Had my psychiatrist not been monitoring my blood tests, I could now be in the hospital with irrepairable damage.

To repeat. The psychiatrist is responsible to order and monitor regular blood testing and react accordingly.