Thank you for your query at DoctorSpring.com
You have been on lithium for 27 years. Now your GFR is 47.
Firstly, lithium does not cause major kidney issues. Yes, the dose needs to be moderated in kidney disease patients. The common side effects of lithium are muscle weakness, fatigue, fine tremor, frequent urination, and thirst can occur and may persist with continued use. Weight gain and swelling from excess fluid can also occur.
Now regarding your GFR, I will need to see your complete report because GFR and creatinine values together indicate the stage of the kidney disease. GFR 47 mostly indicates stage 2/3 kidney disease, depending on the creatinine. Do you have any difficulty passing urine or hematuria?
Please feel free to discuss further,