Hypercalcemia is a condition in which the calcium level in your blood is above normal. Too much calcium in your blood can weaken your bones, create kidney stones, and interfere with the way your heart and brain works.
Hypercalcemia most commonly results from overactive parathyroid glands. These four tiny glands are each about the size of a grain of rice and are located on or near the thyroid gland. Other causes of hypercalcemia include cancer, certain other medical disorders, some medications, and excessive use of calcium and vitamin D supplements.
Signs and symptoms of hypercalcemia may range from nonexistent to severe. Treatment depends on the underlying cause.
You might not experience any signs or symptoms if your hypercalcemia is mild. More-severe cases produce symptoms related to the parts of your body affected by the high calcium levels in your blood. Examples include:
Kidneys. Excess calcium in your blood means your kidneys have to work harder to filter it out. This can cause excessive thirst and frequent urination.
Digestive system. Hypercalcemia can cause stomach upset, nausea, vomiting and constipation.
Bones and muscles. In most cases, the excess calcium in your blood was leached from your bones, which weakens them. This can cause bone pain. Some people who have hypercalcemia also experience muscle weakness.
Brain. Hypercalcemia can interfere with the way your brain works, resulting in confusion, lethargy and fatigue.
When to see a doctor
Contact your doctor if you develop signs and symptoms that may indicate hypercalcemia — such as being extremely thirsty, urinating frequently and having abdominal pain.
In addition to building strong bones, calcium is crucial for the transmission of nerve signals and other functions. If there isn't enough calcium in your blood, your parathyroid glands secrete a hormone that triggers:
Your bones to release calcium into your blood
Your digestive tract to absorb more calcium
Your kidneys to excrete less calcium and activate more vitamin D, which plays a vital role in calcium absorption
This delicate balance between too much and too little calcium in your blood can be disrupted by a variety of factors. Hypercalcemia may be caused by:
Overactive parathyroid glands. The most common cause of hypercalcemia, overactive parathyroid glands (hyperparathyroidism) may stem from a small noncancerous tumor on one or more of the four parathyroid glands.
Cancer. Lung cancer and breast cancer, as well as some cancers of the blood, can increase your risk of hypercalcemia. Spread of cancer (metastasis) to your bones also increases your risk of hypercalcemia.
Other diseases. Certain diseases, such as tuberculosis and sarcoidosis, may raise blood levels of vitamin D, which stimulates your digestive tract to absorb more calcium.
Immobility. People with cancer or other diseases that cause them to spend a great deal of time sitting or lying down may develop hypercalcemia. Over time, bones that don't bear weight release calcium into the blood.
Medications. Certain drugs — such as lithium, which is used to treat bipolar disorder — may increase the release of parathyroid hormone.
Supplements. Taking excessive amounts of calcium or vitamin D supplements over time can raise calcium levels in your blood above normal.
Hereditary factors. A rare genetic disorder known as familial hypocalciuric hypercalcemia causes an increase of calcium in your blood because of faulty calcium receptors in your body.
Dehydration. A common cause of mild or transient hypercalcemia is dehydration, because when there is less fluid in your blood, calcium concentrations rise.
Women in their 50s are the population at highest risk of overactive parathyroid glands.
Hypercalcemia complications may include:
Osteoporosis. If your bones continue to release calcium into your blood, you may develop the bone-thinning disease osteoporosis, which could lead to bone fractures, spinal column curvature and loss of height.
Kidney stones. If your urine contains too much calcium, crystals may form in your kidneys. Over time, the crystals may combine to form kidney stones. Passing a stone can be extremely painful.
Kidney failure. Severe hypercalcemia can damage your kidneys, limiting their ability to cleanse the blood and eliminate fluid.
Nervous system problems. Severe hypercalcemia can lead to confusion, dementia and coma, which can be fatal.
Abnormal heart rhythm (arrhythmia). Hypercalcemia can affect the electrical impulses that regulate your heartbeat, causing your heart to beat irregularly.
Because hypercalcemia may cause few, if any, signs or symptoms, you may not know you have the disorder until routine blood tests show a high level of blood calcium. Blood tests also can reveal whether your parathyroid hormone level is high, indicating that you have hyperparathyroidism.
To determine if your hypercalcemia is caused by an underlying problem, such as cancer or sarcoidosis, your doctor might recommend imaging tests of your bones or lungs.
If your hypercalcemia is mild, you and your doctor may choose to watch and wait, monitoring your bones and kidneys over time to be sure they remain healthy.
In some cases, your doctor may recommend:
Calcimimetics. This type of drug mimics calcium circulating in the blood, so it can help control overactive parathyroid glands.
Bisphosphonates. Intravenous osteoporosis drugs can help rebuild bone weakened by hypercalcemia. Risks associated with this treatment include osteonecrosis of the jaw and certain types of thigh fractures.
Prednisone. If your hypercalcemia is caused by high levels of vitamin D, short-term use of steroid pills such as prednisone might be helpful.
IV fluids and diuretics. Extremely high calcium levels can be a medical emergency. Hospitalization for treatment with IV fluids and diuretics to promptly lower the calcium level may be needed to prevent heart rhythm problems or damage to the nervous system.
Surgical and other procedures
Problems associated with overactive parathyroid glands often can be cured by surgery to remove the malfunctioning tissue. In many cases, only one of a person's four parathyroid glands is affected. A special scanning test uses an injection of a small dose of radioactive material to locate the gland or glands that aren't working properly.
If you develop hypercalcemia, it may be possible to prevent bone and kidney damage by doing the following:
Drink plenty of fluids, especially water. Drinking fluids can help keep you from dehydration and help prevent kidney stones from forming.
Exercise. Once your calcium levels return to normal, and if you're otherwise healthy, it's important to remain active to help maintain bone density. Try to combine strength training with weight-bearing exercises.
Don't smoke. Smoking has been shown to increase bone loss as well as dramatically increase your risk of a number of serious health problems. Talk to your doctor about the best ways to quit.