Wow, I can't believe your doc is not checking your kidney function on lithium. When I first started on it, I was checked & it showed my cretine (sp?) levels were too high so he said to drink lots more water & he would test again. Still too high so he did an ultrasound to make sure there was not a tumor on the kidney causing the problem. No tumor so had to get off the lithium. Too bad as it did wonders for my bipolar. Then began a year long qwest for the right combo of meds that would work for me (currently take 6). Insist on the kidney function test. It says right on the insert that this should be done or ask your pharmacist.--Suzy