Hypercalcemia is when your blood has too much calcium. Your blood normally contains about 1 percent of the calcium in your body and your teeth and bones the remainder. If your blood's calcium level is higher, the excess calcium can cause such symptoms as confusion, fragile bones and nausea.
Primary Hyperparathyroidism
The leading cause of high levels of calcium in the blood is a condition called primary hyperparathyroidism, according to the National Institutes of Health's MedlinePlus website. There are four glands known as parathyroid glands in your neck. The glands produce a substance called parathyroid hormone, which works with another hormone called calcitonin, a product of the thyroid gland, and vitamin D to regulate the amount of calcium in your blood. However, if any of the parathyroid glands become enlarged or develop a growth -- which is typically not cancerous -- they may start to release too much parathyroid hormone. Proper regulation of calcium levels may fail then, leading to excess calcium in your blood.
Certain Cancers
Various types of cancer can make a high level of calcium in your blood more likely, explains MayoClinic.com. Such cancers include multiple myeloma and certain other cancers that affect blood cells, breast cancer and lung cancer. Some cancerous tumors can cause your bones to release calcium into your blood because they produce a protein compound that mimics the actions of parathyroid hormone. In addition, when cancerous cells spread to your bones, they may force calcium into your blood because the cells take up space inside your bones that the calcium normally would. Cancer and primary hyperparathyroidism together cause almost 90 percent of the cases of high calcium levels in the blood, according to the Cleveland Clinic.
Some Medications
Certain medications, such as lithium that is used to manage bipolar disorder, can cause the parathyroid glands to become overactive and release excess parathyroid hormone, leading to a high level of calcium in your blood. Other medications, including thiazide that is used as a diuretic, can cause calcium to build up in your blood because they reduce the level of calcium that exits your body in urine.
Excess Supplements
Also called hypervitaminosis D, an excess amount of vitamin D in your body can interfere with the ability of parathyroid hormone, calcitonin and vitamin D to properly regulate the level of calcium in your blood. A common cause of excess vitamin D is taking too many vitamin D supplements. Similarly, taking too many calcium supplements can also cause the level of calcium in your blood to increase.
Extensive Inactivity
People who spend an abnormal amount of time lying down or sitting -- due to disease, for example -- are at risk of developing a high level of calcium in their blood. When you are bedridden, immobile or insufficiently active for long periods, your bones suffer because they are not bearing weight as the normally do. As a result, they begin to release calcium into your blood.
