Calcium (Ca)

Calcium is one of the most important minerals in your body. About 1% of the calcium in your body is in your blood. The rest is stored in your bones and teeth. Having the right amount of calcium in your blood is necessary for your nerves, muscles, and heart to work properly. It also helps blood vessels move blood throughout your body and helps release hormones that affect many body functions. Calcium also plays a role in helping your blood clot, in supporting bone metabolism, and in regulating enzyme activity. Your blood calcium level is kept in balance by a complex system that includes parathyroid hormone, vitamin D, calcitonin, adrenal cortical steroids, and other hormones.

Your health care provider may have ordered a basic or comprehensive metabolic panel, which includes a calcium blood test, as part of your routine checkup. You may also have this test to diagnose or monitor conditions that can affect your blood calcium or if you have symptoms of abnormal calcium levels.

Results from a total calcium test that are higher than normal (hypercalcemia) may be a sign of conditions affecting your bones, parathyroid glands, thyroid, or kidneys, among others. The two most common causes of high blood calcium are overactive parathyroid glands and certain cancers, including those that have spread to the bones.

Mildly high calcium often causes no symptoms. As levels rise (generally above about 12 mg/dL), people may feel tired, thirsty, nauseated, or constipated. Severely high calcium (above about 14 mg/dL), especially with symptoms like confusion, severe weakness, vomiting, or an irregular heartbeat, is a medical emergency that can affect the heart and brain. Seek prompt medical care if your provider tells you your calcium is very high or you feel suddenly unwell.

Results from a total calcium test that are lower than normal (hypocalcemia) may also be a sign of bone, parathyroid, thyroid, or kidney conditions, vitamin D deficiency, or low magnesium. Very low calcium can cause muscle cramps, tingling around the mouth or fingers, and in severe cases muscle spasms.

If your results from a total calcium blood test are not in the normal range, it doesn't always mean that you have a medical condition that needs treatment. Your diet, your protein and albumin levels, and certain medicines can affect your calcium levels. If you have questions about your results, talk with your provider.