A Case of Hypercalcemia with the Oral Administration of Active Vitamin D3 and Chinese Herbal Medicine

The causes of hypercalcemia vary. There are high-calcium-containing preparations in Chinese herbal medicine, which may contribute to drug-induced hypercalcemia. We encountered a case of hypercalcemia following the simultaneous administration of an active vitamin D3 preparation and several Chinese herbal medicines. The patient had been treated at several medical institutions, with one institution administering eldecalcitol and another institution administering Keishikaryukotsuboreito, Borei powder, and Goreisan. The patient presented with drug-induced hypercalcemia due to an unexpected synergistic effect. Confirmation of prescriptions for patients with multiple medical visits and recognition of the components and side effects of Chinese herbal medicines is thus considered to be extremely important.