High calcium levels in the blood (not urine). This has nothing to do with eating too much calcium and is most often due to an abnormal parathyroid adenoma – a benign growth in the neck which interferes with normal calcium regulation. If a parathyroid adenoma is isolated as the cause of high calcium levels, surgery to remove the adenoma is usually required.
Other causes of hypercalcaemia include some cancers, immobility, sarcoid, some medications (Lithium), excessive intake of calcium supplements and rare hereditary disorders.
It is important to note that many patients with high levels of calcium in the urine (which can cause kidney stones) do NOT have hypercalcaemia (high levels of calcium in the blood).