Is High Calcium a Sign of Cancer?

This page is for anyone told they have high blood calcium (hypercalcemia). It covers what high calcium feels like, its common causes, how cancer can raise it, and what happens next.

Almost nobody feels high calcium and goes to the doctor. It shows up on a blood panel ordered for something else.

MedlinePlus puts it plainly: the condition is most often found at an early stage on routine blood tests, and most people have no symptoms.

That framing matters. You are not reading about a warning sign your body sent you. You are reading about a number that now needs an explanation.

When symptoms do appear, MedlinePlus lists nausea, poor appetite and constipation. It also lists more thirst, passing urine more often, muscle weakness, tiredness, confusion and bone pain.

Describe how you actually feel. Do not wait for the next routine blood test if you feel unwell.

Contact your care team the same day if you notice:

• heavy thirst with much more urine than usual.
• nausea, loss of appetite, or new constipation that will not settle.
• muscle weakness, twitching or unusual tiredness.
• difficulty thinking or speaking clearly.
• new or worsening bone pain.

Call 911 or go to an emergency department if you have:

• confusion or agitation, unusual drowsiness, or you are hard to wake.
• an irregular or racing heartbeat, or a seizure.
• repeated vomiting with little or no urine passing.

The American Cancer Society lists confusion, an irregular heartbeat and seizures as severe signs that need help right away. Untreated high calcium can become life threatening.

MedlinePlus names excess parathyroid hormone as the most common cause. That comes from an enlarged gland or a growth on one, and most of those growths are not cancer.

Other causes it lists:

• being low on fluids, which concentrates the blood.
• too much vitamin D.
• very high calcium supplement intake.
• an overactive thyroid gland.
• chronic kidney disease or kidney failure.
• medicines such as thiazide water tablets and lithium.
• long spells of being immobile.
• some infections and conditions such as tuberculosis, sarcoidosis and Paget disease.

MedlinePlus names some cancers among the causes. It lists lung cancer, breast cancer, and cancer that has spread.

There are two main routes. Cancer growing in bone releases calcium as it breaks the bone down. NCI notes that a tumor can damage bone and raise blood calcium in multiple myeloma.

The second route skips the bone. Some tumors make a protein that acts like parathyroid hormone. That signal alone can push calcium up.

Parathyroid hormone is measured at the same time as calcium.

MedlinePlus lists the usual panel. It covers blood calcium, parathyroid hormone, PTH-related protein (the hormone-like protein some tumors make), vitamin D, and urine calcium.

The American Cancer Society says doctors also check kidney function.

Two things happen in parallel. The level comes down, and the reason gets found.

MedlinePlus calls fluids through a vein the most important treatment when the level is severe. Other options include bone-protecting drugs, calcitonin, steroids, water tablets and dialysis.

When one abnormal parathyroid gland is the cause, surgery fixes the calcium level.

Bring the printed result and any older calcium values. A trend over time tells more than a single number.

List every supplement, including calcium and vitamin D, and every medicine. Note when your symptoms started and what has changed. Lab Tests for Cancer explains how results like this get interpreted.

• MedlinePlus — Hypercalcemia
• American Cancer Society — Hypercalcemia
• National Cancer Institute — Plasma Cell Neoplasms (Including Multiple Myeloma) Treatment (PDQ)