High serum calcium may be caused by physiological factors such as eating too much calcium-containing food, or disease factors such as hyperparathyroidism and vitamin D toxicity, and prompt medical attention is needed to identify the cause. 1. Physiological factors Eating a large amount of calcium-containing foods can cause a transient increase in blood calcium. If the intake of these foods is stopped, it will gradually return to normal. 2. Pathologic factors (1) Hyperparathyroidism: Due to the excessive secretion of parathyroid hormone, blood calcium will also increase, or need to carry out parathyroid function tests to further clarify the cause of the disease. (2) Vitamin D toxicity: if the intake of vitamin D is too much, there are symptoms of toxicity, which can also lead to high serum calcium. (3) Malignant tumor is also a common cause of hypercalcemia. The above are only some of the common causes. If you find high serum calcium, you should consult a doctor in time and follow the doctor’s instructions for standardized treatment after a clear diagnosis.