Just a question- did your doctor run any kind of blood tests or panels [thyroid, kidney, serum level] re:lithium before taking you off the medication?
Because... how well lithium works for an individual is affected by the serum level of the medication in the blood- which can vary from person to person. It is not dictated necessarily by the actual dosage in milligrams. And the precise serum level which works for each individual can vary- though the typical therapeutic range is usually .6-1.1ish.
If no serum level was taken, that's one issue.
Another issue is that kidney and theyroid functions don't just magically go to hell in one night.
They are to be monitored regularly.
There are people who are on lithium for many many many years and don't have problems; they are adequately monitored and it works for them
There is a reason it is often referred to as "the gold standard" when it comes to bipolar medications.
Because it works, it's cheap, easy to manage and monitor... and despite claims to the contrary- if a person takes care of themselves there are not nearly as many bad side effects- nor do they occur as often- as the rumors would have you believe.
I also question that if you were on 600mg, but it was doing nothing... why on it for so long?
But ya know... my two cents, likely worth as much
-Josie