Can multiple myeloma cause high calcium in cancer?

This is called hypercalcaemia of malignancy. It can affect hydration, kidney function, digestion, thinking and heart rhythm, so it should be assessed promptly rather than managed at home.

Myeloma cells can stimulate the breakdown of bone. Calcium then moves from bone into the blood, while dehydration or reduced kidney function may make the level harder for the body to correct. A blood test confirms the calcium level; symptoms alone cannot do this.

Possible features include unusual thirst, frequent urination, constipation, nausea, abdominal discomfort, muscle weakness, tiredness, drowsiness or confusion. These symptoms have other possible causes, but in someone with myeloma they warrant contact with the treating team.

Contact your oncology or haematology team if new symptoms appear or a test shows raised calcium. The team may repeat blood tests, check kidney function and review medicines and fluid intake. Treatment depends on the severity, symptoms and overall condition, and may include intravenous fluids, medicine that slows bone breakdown and treatment directed at the myeloma.

Do not start calcium supplements, stop prescribed medicines or force large amounts of fluid without clinical advice. Bring a current medicines and supplements list to the assessment because some products can influence calcium or kidney function.

Seek urgent medical help for new confusion, marked drowsiness, fainting, severe weakness, repeated vomiting, inability to keep fluids down, very little urine, chest discomfort or an irregular heartbeat. These features can accompany a substantial calcium disturbance, dehydration or another serious problem and require prompt assessment.

Ask what your calcium and kidney results show, whether any medicine or supplement should change, which symptoms should trigger an urgent call, and how the plan will address both the raised calcium and the underlying myeloma.