Hypercalcaemia / High Calcium

What is hypercalcaemia?

Hypercalcaemia is a medical condition in which the level of calcium in the blood is higher than normal. Calcium is vital for many functions in the body, including maintaining strong bones and teeth, supporting muscle contraction, transmitting nerve signals and regulating heart rhythm.

In healthy individuals, calcium levels in the blood are carefully controlled within a narrow range by the parathyroid glands through the kidneys, intestines and vitamin D. When this balance is disrupted, calcium can build up in the bloodstream, leading to hypercalcaemia.

The condition may be mild and temporary or more severe and persistent, depending on the underlying cause. Because calcium affects many organs and systems, maintaining normal blood calcium levels is essential for overall health.

Why is hypercalcaemia a hormone-related problem?

Hypercalcaemia is considered a hormone-related problem because blood calcium levels are normally kept within a very narrow range by endocrine control, primarily through parathyroid hormone (PTH) and vitamin D (calcitriol).

Excessive secretion of PTH, as seen in primary hyperparathyroidism, is the most common cause of hypercalcaemia, as it drives increased calcium release from bone, enhanced kidney calcium retention and greater intestinal absorption via vitamin D activation. Similarly, conditions causing excess vitamin D (such as excessive supplementation, granulomatous disease, or malignancy producing calcitriol) can lead to raised calcium levels. Some cancers also produce PTH-related peptide (PTHrP), which mimics the effects of PTH.

Because these mechanisms involve abnormal hormonal activity rather than simple dietary intake of calcium, hypercalcaemia is fundamentally linked to disturbances in hormonal regulation, most commonly due to abnormal levels of parathyroid hormone.

What causes hypercalcaemia?

Hypercalcaemia develops when the body’s natural control of calcium is disrupted, leading to excess calcium circulating in the blood. The most common and less common causes include:

• Primary hyperparathyroidism — the leading cause of hypercalcaemia, usually due to a benign growth (adenoma) or enlargement of the parathyroid glands. These glands regulate calcium levels, and overactivity results in excessive calcium release from bone and reduced excretion by the kidneys. It also increases levels of Vitamin D which causes excessive calcium absorption by the gut. 

• Cancer — certain cancers, such as lung, breast and multiple myeloma, can cause high calcium levels. This may occur through bone breakdown (metastatic spread to bone) or secretion of hormone-like substances that raise calcium levels. Dr. Dinesh says this is the second most common cause of hypercalcaemia and something that must be ruled out. 

• Excess vitamin D or calcium intake — overuse of vitamin D supplements, calcium tablets or antacids can lead to increased absorption of calcium from the gut.

• Medications — drugs such as thiazide diuretics (used for blood pressure) and lithium (used in psychiatric treatment) can raise calcium levels.

• Other medical conditions — diseases such as sarcoidosis and tuberculosis may cause the body to produce excess vitamin D, increasing calcium absorption. Prolonged inactivity or immobilisation can also lead to bone calcium release.

The exact cause of hypercalcaemia must be identified, as treatment depends on correcting the underlying problem.

What is the difference between hypercalcaemia and hypocalcaemia?

Calcium levels in the blood are normally kept within a narrow range, as both excess and deficiency can disrupt vital body functions. Hypercalcaemia refers to abnormally high levels of calcium in the blood, whereas hypocalcaemia describes abnormally low levels. 

Although they affect the same mineral, the two conditions differ significantly in their underlying causes, clinical features and potential complications.

Feature	Hypercalcaemia (high calcium)	Hypocalcaemia (low calcium)
Definition	Blood calcium levels are above normal	Blood calcium levels are below normal
Common causes	Overactive parathyroid glands (primary hyperparathyroidism), cancers, excess vitamin D or calcium, certain medications (e.g. thiazides, lithium)	Vitamin D deficiency, chronic kidney disease, underactive parathyroid glands (hypoparathyroidism), certain medications (e.g. bisphosphonates)
Key symptoms	Thirst and frequent urination, constipation, abdominal pain, nausea, bone pain, confusion, irregular heartbeat	Tingling or numbness in fingers and lips, muscle cramps or spasms, fatigue, seizures in severe cases
Main risks	Kidney stones, osteoporosis, kidney failure, cardiac arrhythmias, coma	Muscle spasms affecting breathing, seizures, abnormal heart rhythms
Treatment focus	Lowering calcium levels with fluids, medicines, or surgery and addressing the underlying cause	Replacing calcium and vitamin D and treating the underlying cause

What are the symptoms of hypercalcaemia?

The symptoms of hypercalcaemia vary depending on how high the blood calcium levels are and how quickly they rise. Mild cases may cause no obvious signs, while more severe cases can affect multiple organs and body systems.

• Mild hypercalcaemia — often produces few or no symptoms and may only be detected during a routine blood test. Some people may experience fatigue, mild muscle weakness, or subtle digestive upset.

• Moderate hypercalcaemia — can cause more noticeable problems, including:
  • Increased thirst and frequent urination
  • Nausea, vomiting, or constipation
  • Abdominal pain or loss of appetite
  • Muscle weakness and joint aches
  • Difficulty concentrating, irritability, or low mood

• Severe hypercalcaemia — high calcium levels can become dangerous and may lead to:
  • Confusion, drowsiness, or altered mental state
  • Irregular heart rhythm (arrhythmia)
  • Severe dehydration
  • Kidney stones or kidney impairment
  • Bone pain and fragility
  • In extreme cases, coma or cardiac arrest

Because symptoms can be vague and overlap with other conditions, blood tests are essential for confirming hypercalcaemia.

Who is at risk of hypercalcaemia in Singapore?

Hypercalcaemia can affect anyone, but certain groups of people are more likely to develop the condition:

• People with overactive parathyroid glands — primary hyperparathyroidism, often caused by a benign parathyroid tumour, is the leading cause of persistent hypercalcaemia. It is most common in middle-aged and older women.

• Patients with cancer — certain cancers, including lung, breast, kidney and multiple myeloma, increase the risk of high calcium levels either through bone destruction or hormone-like effects.

• Individuals with a family history — genetic conditions such as familial hypocalciuric hypercalcaemia can raise calcium levels and run in families (thankfully benign).

• Those with long-term immobility — people confined to bed rest or with reduced mobility may develop hypercalcaemia as calcium is released from bones.

• Patients taking certain medications — thiazide diuretics, lithium and excessive use of calcium or vitamin D supplements can contribute to hypercalcaemia.

• People with chronic medical conditions — diseases such as sarcoidosis or tuberculosis may raise vitamin D activity in the body, increasing calcium absorption. Kidney disease can also impair calcium regulation.

Identifying those at higher risk allows for earlier detection and management, preventing serious complications.

What are the complications of hypercalcaemia?

If left untreated, hypercalcaemia can lead to serious health problems, as persistently high calcium levels place stress on multiple organs and systems.

• Kidney problems — high calcium can reduce the kidneys’ ability to concentrate urine, leading to dehydration, excessive urination and kidney stones. Over time, it may cause chronic kidney damage or kidney failure.

• Bone loss (osteoporosis) — when calcium is continually released from bone into the bloodstream, bones become weaker, thinner and more prone to fractures.

• Heart complications — severe hypercalcaemia can affect the heart’s electrical activity, causing arrhythmias (irregular heartbeats) and, in rare cases, cardiac arrest.

• Neurological effects — high calcium levels can interfere with normal brain function, leading to confusion, fatigue, depression, or, in advanced cases, reduced consciousness and coma.

• Digestive issues — long-term hypercalcaemia may cause abdominal pain, constipation, nausea or pancreatitis in some patients.

Because of these risks, hypercalcaemia should always be investigated and managed promptly.

How is hypercalcaemia diagnosed?

Hypercalcaemia is usually suspected when patients present with symptoms such as fatigue, thirst, or abdominal discomfort, but it is often first detected through a routine blood test. Diagnosis involves confirming high calcium levels and identifying the underlying cause.

• Blood tests — a simple blood test can measure total serum calcium and sometimes ionised calcium (the active form). It is imperative to check parathyroid hormone (PTH) levels to determine whether the hypercalcaemia is caused by overactive parathyroid glands. If it is not due to high PTH levels, cancer must be ruled out. Other useful tests may include vitamin D, kidney function and phosphate levels.

• Urine tests — a 24-hour urine collection can help assess how much calcium is being excreted, which provides clues about whether the problem is related to excessive intake, bone release or kidney handling of calcium. This test also rules out an important cause of hypercalcaemia that is benign-FHH.

• Imaging tests — X-rays, ultrasound, or CT scans may be used to look for kidney stones, bone loss, or tumours that might be contributing to high calcium levels. A parathyroid scan and  neck ultrasound may be performed if primary hyperparathyroidism is suspected.

• Medical history and examination — doctors will ask about symptoms, medications, family history, diet and any medical conditions that could raise calcium levels.

Accurate diagnosis is crucial, as treatment needs to target the specific cause of hypercalcaemia rather than just lowering calcium levels temporarily.

What are the treatment options for hypercalcaemia? 

Treatment of hypercalcaemia depends on how high the calcium level is, how quickly it developed and what is causing it. Mild cases without symptoms may only need monitoring, while more severe cases require urgent hospital care.

• Treating the underlying cause — long-term management focuses on correcting the reason for high calcium, such as removing an overactive parathyroid gland, adjusting medications or treating cancer.

• Fluids and hydration — Intravenous fluids (saline) are often given in hospitals to rehydrate the body and help the kidneys flush excess calcium from the blood, but this is a temporary fix.

• Medications 

• Bisphosphonates (e.g. zoledronic acid) or denosumab may be used to reduce calcium release from bones.

• Calcitonin can temporarily lower calcium by helping it move back into bone and increasing kidney excretion and is used as an interim measure in severe causes.

• Steroids are sometimes prescribed if hypercalcaemia is due to excess vitamin D activity, as in sarcoidosis or oversupplementation.

• Dialysis — in severe or resistant cases, particularly when kidney function is impaired, dialysis may be required to rapidly lower calcium levels.

With prompt treatment, calcium levels can usually be brought under control. Ongoing care may involve regular monitoring and lifestyle adjustments to prevent recurrence.

Summary 

Hypercalcaemia, or high calcium levels in the blood, is a condition that can range from mild and symptom-free to severe and life-threatening. It is most often caused by overactive parathyroid glands or certain cancers, but can also result from medications, vitamin D or calcium excess or other medical conditions. Symptoms may include fatigue, thirst, frequent urination, nausea, constipation, confusion and, in severe cases, kidney failure or heart rhythm disturbances.

If you have concerns about high calcium levels, schedule a consultation with us at The Metabolic Clinic for detailed assessment, personalised treatment and ongoing care to help you restore balance and protect your long-term health.

Frequently Asked Questions (FAQs)