For over half a century, it has been widely known that lithium is the most efficacious maintenance treatment for bipolar disorder. Despite thorough research on the long-term effects of lithium on renal function, a number of important questions relevant to clinical practice remain. The risk of polyuria, reflecting renal tubular dysfunction, is seen in a substantial proportion of patients treated with long term lithium therapy. The duration of lithium may be the most important risk factor for lithium-induced polyuria. Most, but not all, studies find that lithium is associated with higher rates of chronic kidney disease compared to either age matched controls or patients treated with other mood stabilizers. Age, duration of lithium therapy and medical disorders such as hypertension and diabetes mellitus are risk factors for chronic kidney disease in lithium-treated patients. The relationship between polyuria and chronic kidney disease is inconsistent but poorly studied. Although not all studies agree, it is likely that lithium may increase the risk for end stage renal disease but in a very small proportion of treated patients. Patients whose renal function is relatively preserved will show either no progression or improvement of renal function after lithium discontinuation. In contrast, patients with more renal damage frequently show continued deterioration of renal function even after lithium discontinuation. Optimal management of lithium treatment requires obtaining a baseline measure of renal function (typically estimated glomerular filtration rate [eGFR]) and regular monitoring of eGFR during treatment. Should the eGFR fall rapidly or below 60 ml/minute, patients should consider a consultation with a nephrologist. A decision as to whether lithium should be discontinued due to progressive renal insufficiency should be made using a risk/benefit analysis that takes into account other potential etiologies of renal dysfunction, current renal function, and the efficacy of lithium in that individual patient.