The case follows the treatment of a woman from age 73 to age 83 who was bipolar and who also had Chronic Kidney Disease (CKD). During the study, the eGFR dropped from 43 to below 20. Initially the treatment was fairly standard but highlighted the difficulty of knowing when to reduce the lithium dose before undesired mood changes occurred. In phase 2 of the treatment, the usual monthly blood serum test is combined with a new concept of a monthly running average eGFR to decide when to reduce the lithium dose. A new way of administering lithium was created which was used when the patient’s daily dose of lithium reached 300mg a day. In place of a fixed daily dose of lithium, a fixed average daily dose of lithium over a short cyclic pattern was used. The daily dose varies within the repeatable cycle but is smoothed out by the long half-life of lithium. The new method allows for the reduction of the lithium dose by small amounts, less than the minimum strength 150mg capsule used in North America or the 100mg tablet used in Europe. The method has been successfully used for several years with the patient’s moods stable and lithium toxicity avoided. The patient is currently on an average daily dose of 187mg a day with an eGFR less than 20.