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What causes high calcium? Diagnosis, prevention, and treatment

Medically reviewed by Anne Jacobson, MD, MPH
Board-Certified Family Physician
Updated May. 8, 2024  •  Published Aug. 7, 2023
Fact Checked
What causes high calcium? Diagnosis, prevention, and treatment
In this article:

Overview: What is high calcium?

Although calcium is essential to the body’s health, too much calcium in the bloodstream is problematic. Most calcium in the body is locked up in the bones, but calcium also circulates in the bloodstream. A delicate system involving parathyroid hormones and vitamin D (calcitriol) keeps calcium levels in the bloodstream within a certain range. When this system fails, calcium levels can rise above the normal range and start causing problems throughout the body, including the digestive system, bones, kidneys, and nervous system. Left untreated, high calcium can result in complications like kidney stones, kidney failure, osteoporosis, bone breaks, arthritis, digestive problems, confusion, coma, muscle weakness, and heart rhythm irregularities.

Key takeaways:

  • High calcium is a common health condition affecting anyone regardless of age, sex, race, or ethnicity. 

  • Overactive parathyroid glands, some types of cancer, excess vitamin D, hormonal disorders, genetic disorders, excessive vitamin A intake, and medication side effects cause high calcium. 

  • Risk factors for high calcium include female sex, age older than 50, a cancer diagnosis, kidney disease, or a family history of high calcium.

  • Symptoms of high calcium include digestive system complaints (nausea, vomiting, stomach pain, constipation), bone problems (bone pain, fractures, arthritis), kidney problems (frequent urination, dehydration, excessive thirst, kidney pain), feeling sick or tired, problems thinking, confusion, irritability, and depression. Severe hypercalcemia can have symptoms such as psychosis, reduced kidney function, muscle weakness, and coma.

  • High calcium requires a medical diagnosis.

  • High calcium generally requires treatment. It typically resolves with treatment, but the timeline will vary depending on the cause.

  • Treatment of high calcium may include treating the underlying cause, fluid intake, prescription medications, or, in severe cases, dialysis.

  • High calcium can sometimes be prevented by restricting calcium or vitamin D intake.

  • Use coupons for high calcium treatments, Lasix (furosemide), Reclast (zoledronic acid), Sensipar (cinacalcet), and Zemplar (paricalcitol) to save up to 80%.

RELATED: Hypercalcemia symptoms: What are the early signs of hypercalcemia?

What causes high calcium?

The most common cause of high calcium is high parathyroid hormone (PTH) levels due to an overactive parathyroid gland. Cancer is the second most common cause of hypercalcemia. Together, both causes account for 90% of high calcium cases.

Overactive parathyroid glands can be caused by:

  • Cancerous or noncancerous growths on the parathyroid gland

  • Genetic disorders

  • Severe vitamin D deficiency

  • Kidney failure

About 1 in 5 people with cancer will have high serum calcium levels, a condition called hypercalcemia of malignancy. The cancer with the highest incidence of hypercalcemia is multiple myeloma, but other cancers can also bring on high blood calcium:

High calcium can also be brought on by excessive amounts of vitamin D in the body, usually caused by excessive vitamin D intake. Other possible causes of elevated vitamin D include sarcoidosis and tuberculosis. 

Other causes of high calcium include:

  • Excessive calcium intake

  • Excessive vitamin A intake

  • Hormone disorders such as severe overactive thyroid gland (thyroid storm) or adrenal gland problems

  • Some rare genetic disorders

  • Paget’s disease of bone

  • Milk-alkali syndrome, an excessive intake of calcium carbonate supplements or antacids

  • Side effects of medications, including thiazide diuretics and lithium

  • Long-term immobilization can cause the body to reabsorb calcium from the bones, raising serum calcium levels. 

Risk factors for high calcium

The most common risk factors for hypercalcemia are:

  • Overactive parathyroid glands

  • Female sex

  • Age older than 50

  • Excessive vitamin D intake

  • Use of calcium supplements or antacids, mainly calcium carbonate

  • Excessive vitamin A intake

  • Family history of high calcium

  • Cancer

  • Thyroid disease

  • Adrenal gland problems

  • Kidney disease

  • Injuries or medical conditions that can result in prolonged immobilization

  • Use of certain medications, such as lithium or thiazide diuretics

RELATED: Can you take too much vitamin D?

Is high calcium serious? When to see a doctor

Healthcare professionals take high calcium very seriously. Moderate to severe high calcium can eventually cause renal failure, heart arrhythmias, and osteoporosis. While mild cases may not cause problems or have difficulties, there is a risk that calcium levels could go up in the future. Also, high calcium levels may indicate a more serious health condition such as cancer or a hormone disorder. 

See your primary care physician or other healthcare provider if experiencing any of the symptoms of high calcium. When high calcium starts damaging the body, the classic symptoms are excessive urination, bone problems, digestive system complaints, feeling sick, and nervous system issues like irritability and brain fog. 

Go to an emergency room for severe symptoms such as confusion, coma, hallucinations, delusions, heartbeat irregularities, or significant muscle weakness.

How is high calcium diagnosed?

High calcium is diagnosed from a blood test measuring total calcium and free calcium levels. Most people with high calcium will have no symptoms, so an unusual calcium reading on a blood test is typically the earliest sign of hypercalcemia. 

If calcium levels are high, the healthcare provider will take a medical history and physical examination to discover the cause. Expect questions like:

  • Do you take supplements?

  • Do you use antacids?

  • Do you have symptoms?

  • What medications do you take?

Additional blood tests will measure parathyroid hormone levels, other hormone levels, and markers in the blood that are typical of cancer. If an overactive parathyroid is the cause, the healthcare provider may order a scan of the parathyroid glands. This scan uses a safe radioactive substance that is only taken up by overactive parathyroid glands, which can then be identified. 

Is high calcium hereditary? 

High calcium can be caused by a few uncommon or rare genetic disorders:

  • Familial hypocalciuric hypercalcemia, which causes the parathyroid to produce excess parathyroid hormone

  • Multiple endocrine neoplasia, a rare inherited disorder that causes parathyroid growths and overactive parathyroid

  • Williams-Beuren syndrome

  • Murk Jansen syndrome

Familial hypocalciuric hypercalcemia is the most common genetic disorder that causes high calcium, but it is still rare (1 in 78,000). Although FHH raises calcium levels, it usually causes only mild hypercalcemia without any symptoms. Most people with FHH do not require treatment.

Is high calcium curable?

Mild and moderate hypercalcemia usually don’t require treatment if there are no symptoms. But it’s important to prevent a further rise in calcium by avoiding antacids and calcium supplements, adjusting the dose of any medications that may be contributing, and continuing to monitor calcium levels. 

If blood calcium levels are high enough to cause symptoms, healthcare providers will immediately try to restore normal calcium levels by using: 

Healthcare professionals may need to treat the underlying cause of hypercalcemia, such as cancer, overactive parathyroid glands, or hormone disorders. If high calcium is being caused by primary hyperparathyroidism, a surgeon will remove one or more of the parathyroid glands. Hypercalcemia of malignancy will require appropriate cancer treatments. If high calcium is a side effect of medication or supplement use, the medication or supplement will be stopped. 

How to prevent high calcium

Many causes of high calcium, such as cancer or overactive parathyroid glands, are difficult to prevent. However, some cases of high blood calcium are preventable by practicing a few sensible precautions. These are especially important to follow when calcium levels are a bit on the high side but not bad enough to cause symptoms or complications:

  • Go easy on the calcium—do not exceed more than 1000 mg of calcium per day

  • Avoid taking too many calcium-based antacids

  • Go easy on the vitamin D supplements except under the advice of a healthcare provider

  • If calcium is high, ask a healthcare provider for a suggested daily intake of calcium and vitamin D

  • Drink plenty of fluids throughout the day to avoid dehydration

Most importantly, get regular checkups

Most people with high blood calcium levels—or any other electrolyte imbalance—don’t notice any symptoms until levels are dangerously high. For this reason, it’s more common to discover high calcium on a routine blood test. Since high calcium can indicate a more serious health condition, getting regular blood tests is important, especially if you have risk factors for high calcium. Even if the cause is benign, knowing it can help you avoid more severe hypercalcemia.

FAQs about high calcium causes

A high coronary artery calcification (Agatston) score measures calcification in the coronary arteries due to plaque buildup. The Agatston score corresponds with the probability of a future heart attack. Artery calcification is a later stage in atherosclerosis, but it is unrelated to high calcium levels in the blood. Atherosclerosis itself can be partly reversed with dramatic changes in diet and exercise. Otherwise, the standard treatments are cholesterol-lowering drugs and surgery.

RELATED: What are the warning signs of clogged arteries?

What medications cause high calcium?

High calcium is a side effect of a few drugs, including lithium and thiazide diuretics. Excessive intake of vitamin D or calcium supplements can also increase calcium levels. Antacids that contain calcium and alkali, such as Tums (calcium carbonate), are much more likely to cause high calcium than other calcium sources. 

Does high calcium mean clogged arteries?

High blood calcium is not the same as calcium buildup in the arteries. High blood calcium only describes the amount of calcium in the bloodstream. Calcium buildup in the arteries, or “artery calcification,” is an accumulation of calcium attaching to the plaque already accumulating on artery walls. Artery calcification is not a complication of high blood calcium levels but rather a complication of high cholesterol and high blood pressure.

What’s next? Additional resources for people with high calcium

Test and diagnostics

Treatments

Scientific studies and clinical trials

Lea este artículo en español aquí.

Medically reviewed by Anne Jacobson, MD, MPH
Board-Certified Family Physician

Anne Jacobson, MD, MPH, is a board-certified family physician, writer, editor, teacher, and consultant. She is a graduate of University of Wisconsin School of Medicine and Public Health, and trained at West Suburban Family Medicine in Oak Park, Illinois. She later completed a fellowship in community medicine at PCC Community Wellness and a master's in Public Health at the University of Illinois-Chicago. She lives with her family near Chicago.

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