Hypercalcemia or high calcium levels may not cause any symptoms. However, serious hypercalcemia can cause excessive thirst, stomach pain, and confusion, among other symptoms.

High calcium levels in the blood (hypercalcemia) can result from an overactive parathyroid gland, too much vitamin D, some medications, and various underlying conditions, including cancer.

Calcium plays an essential role in the body. It helps build strong bones and teeth while also supporting the muscles, nerves, and heart. However, too much calcium can lead to problems.

In this article, we explore the symptoms, causes, and complications of hypercalcemia. We also describe how doctors diagnose and treat hypercalcemia.

diagram of parathyroid glands which control calcium in the blood and may lead to hypercalcemiaShare on Pinterest
The parathyroid glands control calcium levels in the blood.

The parathyroid glands are responsible for controlling calcium levels in the blood. These four tiny glands sit behind the thyroid gland.

When the body needs calcium, the parathyroid glands secrete a hormone. This hormone signals:

  • the bones to release calcium into the blood
  • the kidneys to excrete less calcium into the urine
  • the kidneys to activate vitamin D, which helps the digestive tract absorb more calcium

Overactive parathyroid glands or an underlying health condition can disrupt the balance of calcium.

If calcium levels become too high, a person may receive a diagnosis of hypercalcemia. This condition can impede bodily functions and may specifically lead to:

Extremely high levels of calcium in the blood can become life threatening.

Mild hypercalcemia may not produce any symptoms, but more serious hypercalcemia can cause:

Various underlying conditions and other factors can cause hypercalcemia. These include:

Overactive parathyroid glands

The parathyroid glands control calcium levels. If they work too hard, this can lead to hypercalcemia.

The parathyroid glands may become overactive when one becomes enlarged or develops a noncancerous growth.

Hyperparathyroidism is the term for having overactive parathyroid glands. It may be the most common cause of hypercalcemia.

Doctors usually diagnose hyperparathyroidism in people aged 50–60 years. It is also three or four times more common in females than in males.

Too much vitamin D

Vitamin D triggers calcium absorption in the gut, allowing this nutrient to enter the bloodstream.

The body usually only absorbs 10–20% of the calcium in the diet, passing the rest out in stools. However, excessive amounts of vitamin D cause the body to absorb more calcium, leading to hypercalcemia.

Some research suggests that therapeutic, high dosage vitamin D supplementation has the potential to cause hypercalcemia. Doctors may recommend these supplements to help treat multiple sclerosis and other conditions.

The Office of Dietary Supplements defines a high dosage of vitamin D as 4,000 international units (IU) or more per day. The recommended daily dose for adults is 600–800 IU per day.


Some types of cancer may cause hypercalcemia. Cancers that commonly lead to this condition include:

In 2021, researchers estimated that hypercalcemia affects about 2% of all cancer patients in the United States each year. This percentage is lower among children.

If cancer spreads to the bone, the risk of hypercalcemia increases.

Other health conditions

Other conditions that may cause high blood levels of calcium include:

Reduced mobility

People who go for an extended period without being able to move around may also have an increased risk of hypercalcemia. When the bones have less work to do, they can weaken and release more calcium into the bloodstream.

Severe dehydration

People who are severely dehydrated have less water in their blood, which can increase the concentration of calcium. However, this imbalance is usually treatable once a person rehydrates sufficiently.

In some cases, high levels of calcium can lead to severe dehydration. It is important for doctors to identify which came first: the high levels of calcium or the dehydration.


Some medications can overstimulate the parathyroid gland, and this can lead to hypercalcemia. One example is lithium, which people sometimes take to treat bipolar disorder.

Without proper treatment, hypercalcemia can contribute to several health conditions.


Over time, the bones may release excessive amounts of calcium into the bloodstream, which makes them thinner, or less dense. The continued release of calcium can lead to osteoporosis.

People with osteoporosis have an increased risk of:

  • fractures
  • significant disability
  • loss of independence
  • prolonged immobility
  • a curvature of the spine
  • becoming shorter over time

Kidney stones

People with hypercalcemia are at risk of developing calcium crystals in their kidneys. These crystals can become kidney stones, which are often very painful. They can also lead to kidney damage.

Kidney failure

Over time, severe hypercalcemia can stop a person’s kidneys from working correctly. The kidneys may become less effective in cleaning the blood, producing urine, and efficiently removing fluid from the body. This is called kidney failure.

An irregular heartbeat

The heart beats when electrical impulses move through it and cause it to contract. Calcium plays a role in regulating this process, and too much calcium can lead to an irregular heartbeat.

Anyone experiencing symptoms of hypercalcemia should speak with a doctor, who will order a blood test and make a diagnosis based on the results.

A person with mild hypercalcemia may have no symptoms, and doctors might only diagnose the condition after carrying out a routine blood test.

The test will check the blood levels of calcium and parathyroid hormone. The results can show how well some of the body’s systems — such as those involving the blood and kidneys — are functioning.

After diagnosing hypercalcemia, a doctor may perform further tests, such as:

  • an electrocardiogram (EKG) to record the electrical activity of the heart
  • a chest X-ray to check for lung cancer or infections
  • a mammogram to check for breast cancer
  • a CT or MRI scan to examine the body’s structure and organs
  • dual-energy X-ray absorptiometry, commonly known as a DEXA scan, to measure bone density

People with mild hypercalcemia may not require treatment, and calcium levels may return to normal over time. The doctor will monitor these levels and the health of the kidneys.

If calcium levels continue to rise or do not improve on their own, doctors may recommend further testing.

For people with more severe hypercalcemia, it is important to discover the cause. The doctor may also offer treatments to help lower calcium levels and prevent complications. Possible treatments include intravenous fluids and medications such as calcitonin or bisphosphonates.

If hypercalcemia is due to overactive parathyroid glands, too much vitamin D, or another health condition, the doctor will also treat the condition responsible.

A person with a noncancerous growth on a parathyroid gland may require surgery to remove it.

Certain lifestyle adjustments can help keep calcium levels balanced and bones healthy. These include:

  • Drinking plenty of water: Staying hydrated may lower blood calcium levels, and it can help prevent kidney stones.
  • Quitting smoking, if applicable: Smoking can increase bone loss. In addition to improving the health of the bones, quitting will reduce the risk of cancer and other health problems.
  • Exercising, including strength training: Resistance training promotes bone strength and health.
  • Following guidelines for medications and supplements: Following medical advice may decrease the risk of consuming too much vitamin D and developing hypercalcemia.

The outlook for people with hypercalcemia depends on its cause and severity.

Mild hypercalcemia may not require treatment. However, if the condition is more serious, a doctor may prescribe medications that lower the levels of calcium and treat the underlying cause.

Anyone experiencing symptoms of hypercalcemia should speak with a doctor.

Hypercalcemia refers to elevated levels of calcium in the blood. Doctors may discover these increased levels when testing for other conditions.

The possible causes of hypercalcemia include an overactive parathyroid gland, certain medications, too much vitamin D, and underlying health conditions, such as cancer.

The treatment options for hypercalcemia will depend on its severity and cause.