Background: The risk of cancer with hypercalcaemia in primary care is unknown.
Methods: This was a cohort study using calcium results in patients aged ⩾40 years in a primary care electronic data set. Diagnoses of cancer in the following year were identified.
Results: Participants (54 267) had calcium results: 1674 (3%) were ⩾2.6 mmol l(-1). Hypercalcaemia was strongly associated with cancer, especially in males: OR 2.92, 95% CI 2.17-3.93, P=<0.001; positive predictive value (PPV) 11.5%; females: OR 1.86, 95% CI 1.39-2.50, P<0.001: PPV 4.1%.
Conclusions: Hypercalcaemia is strongly associated with cancer in primary care, with men at most risk, despite hypercalcaemia being more common in women.