The purpose of this study was to ascertain the prevalence of hypercalcaemia and hyperparathyroidism in individuals on long term lithium therapy who were monitored by their general practitioners and living within the West Galway mental health catchment area. We also wished to assess the extent of screening for calcium dysfunction in this patient cohort.Current guidelines do not specify the need for calcium monitoring in patients on lithium therapy. We conducted a retrospective analysis of clinical and laboratory data collected as part of regular monitoring for patients on long term lithium treatment. Three hundred and thirty three patients had serum lithium levels monitored over a 2 year period. Fifteen patients (5.3%) had lithium associated hypercalcaemia. The mean duration of lithium treatment for those with hypercalcaemia was 15 years and these patients had a mean serum calcium level of 2.7mmol/L. Eighty six (14%) patients did not have a calcium level monitored over the 2 year period. Three patients (1%) were found to have hyperparathyroidism. This survey supports the need for regular monitoring of serum calcium levels in patients on maintenance lithium treatment.