What Happens If Calcium Is Too High? Understanding Hypercalcemia

December 12, 2025 •

3 min read

Hypercalcemia, the medical term for having too much calcium in your blood, affects approximately 1-2% of the population, with many cases being detected incidentally during routine blood work. It is crucial to understand what happens if calcium is too high, as elevated levels can lead to serious issues impacting the kidneys, bones, and heart.

Quick Summary

Excessive blood calcium can weaken bones, impair kidney function leading to kidney stones, and disrupt heart and brain activity. This condition, known as hypercalcemia, is most often caused by an overactive parathyroid gland or certain cancers.

Key Points

Hypercalcemia is High Blood Calcium: The medical condition known as hypercalcemia occurs when calcium levels in the blood are abnormally elevated.
Diverse Symptoms: Manifestations of high calcium can vary widely, affecting the digestive system (constipation), kidneys (excessive urination), bones (pain), and nervous system (confusion, fatigue).
Common Causes: The two most frequent causes are an overactive parathyroid gland (hyperparathyroidism) and certain types of cancer.
Serious Complications: Untreated or severe hypercalcemia can lead to serious problems, including kidney stones, bone fractures, and life-threatening heart arrhythmias or coma.
Targeted Treatment: Management depends on the cause, ranging from dietary changes and hydration for mild cases to medications like bisphosphonates or even surgery for more severe conditions.
Early Detection is Key: Since mild hypercalcemia can be asymptomatic, routine blood tests often catch the condition early, allowing for timely intervention and better prognosis.

What Is Hypercalcemia?

Calcium is a vital mineral essential for bone health, nerve function, muscle contraction, and blood clotting. The body maintains a narrow range of blood calcium levels through hormones like parathyroid hormone (PTH) and calcitonin. Hypercalcemia occurs when blood calcium rises above the normal range. Mild cases might not show symptoms and are found during routine tests, while more severe hypercalcemia can affect multiple body systems.

Symptoms of High Calcium

The symptoms of hypercalcemia depend on its severity and speed of onset. The classic signs are sometimes recalled with the mnemonic "stones, bones, groans, moans, and psychiatric overtones".

Potential Symptoms

Gastrointestinal: Nausea, vomiting, constipation, abdominal pain, and reduced appetite.
Kidney-Related: Increased thirst and frequent urination, as well as the potential for kidney stones.
Bone and Muscle: Bone pain, muscle weakness, and aches. Chronic high calcium can lead to osteoporosis.
Neurological: Fatigue, confusion, memory issues, depression, and irritability. Severe cases can result in stupor or coma.
Cardiac: Irregular heartbeat and high blood pressure.

Common Causes of Hypercalcemia

The most frequent causes are primary hyperparathyroidism and certain cancers.

Primary Hyperparathyroidism

This is the leading cause in the general population. It involves overactive parathyroid glands producing excess PTH, which increases calcium release from bones and reduces kidney excretion of calcium.

Malignancy (Cancer)

Cancer is a common cause, particularly in hospital settings. Mechanisms include:

Humoral Hypercalcemia of Malignancy (HHM): Tumors releasing PTH-related peptide (PTHrP) that acts like PTH.
Osteolytic Hypercalcemia: Cancer spreading to bones and causing their destruction.

Other Causes

Vitamin D Toxicity: Excessive vitamin D intake.
Medications: Drugs like lithium and thiazide diuretics.
Granulomatous Diseases: Conditions increasing active vitamin D.
Severe Dehydration: Concentrating blood calcium levels.
Prolonged Immobilization: Calcium release from bones due to lack of weight-bearing.

Effects of High Calcium on the Body

Persistent or severe hypercalcemia can harm several organ systems.

Organ System Impacts

Kidneys: Risk of kidney stones, impaired kidney function, and potential kidney failure. Calcium salt deposits (nephrocalcinosis) can also occur.
Bones: Weakening of bones (osteoporosis), increased risk of fractures, and potential bone cysts.
Heart: Interference with heart rhythm (arrhythmias) and high blood pressure.
Nervous System: Cognitive issues like confusion and memory loss. Severe cases can lead to coma.

Comparison of Common Causes


Feature	Primary Hyperparathyroidism	Malignancy-Induced Hypercalcemia
Onset	Usually gradual	Often rapid and more severe
Symptom Severity	Frequently mild or asymptomatic	More pronounced
Underlying Issue	Overactive parathyroid gland(s)	Release of PTHrP or bone destruction by cancer
PTH Levels	Elevated or inappropriately normal	Typically suppressed
Prognosis	Generally good with treatment	Often indicates advanced disease

Treatment Options

Treatment for hypercalcemia depends on the underlying cause and severity.

Management Approaches

Mild Cases: Often managed with observation, increased fluid intake, avoiding calcium/vitamin D supplements, and staying active.
Medications: Intravenous fluids are crucial for severe cases. Bisphosphonates inhibit bone breakdown. Calcimimetics like Cinacalcet reduce PTH release. Corticosteroids can help in cases linked to excess vitamin D. Denosumab may be used for severe cancer-related cases unresponsive to bisphosphonates.
Surgery: Removing the overactive parathyroid gland is often effective for primary hyperparathyroidism.

Conclusion

Elevated calcium levels, or hypercalcemia, pose potential health risks, ranging from subtle symptoms to severe complications affecting multiple organ systems. Primary hyperparathyroidism and cancer are the most frequent culprits. Identifying the root cause is vital for appropriate treatment. While mild cases may require simple lifestyle adjustments, more significant hypercalcemia necessitates prompt medical intervention. If you experience symptoms suggestive of high calcium, consult a healthcare provider for evaluation. Additional details on hypercalcemia symptoms and causes are available from resources like the Mayo Clinic.

Frequently Asked Questions

The most common cause is primary hyperparathyroidism, a condition where one or more of the four parathyroid glands in the neck become overactive and produce too much parathyroid hormone.

Yes, excessive intake of calcium or vitamin D supplements over time can lead to high calcium levels in the blood. Overuse of calcium-based antacids can also contribute.

High calcium forces the kidneys to work harder to filter the blood, which can lead to excessive urination and thirst. Over time, it can cause calcium crystals to form painful kidney stones or even lead to kidney damage and failure.

Neurological symptoms can include fatigue, drowsiness, confusion, memory problems, depression, and irritability. In severe cases, it can cause more serious issues like stupor or coma.

No, while cancer is a significant cause of hypercalcemia, especially in hospital settings, it is not the only cause. Primary hyperparathyroidism is a more frequent cause in the general population.

Mild cases, particularly if asymptomatic, may not require immediate treatment. Instead, a doctor might recommend monitoring the condition, drinking more water, and avoiding excess calcium or vitamin D supplements.

Severe hypercalcemia is a medical emergency requiring hospitalization. Treatment often includes intravenous fluids to flush out excess calcium, followed by medications like bisphosphonates to curb bone resorption.

Yes, high calcium levels can interfere with the electrical signals controlling the heart, potentially causing an irregular heartbeat (arrhythmia), which can be life-threatening.