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High calcium in people with cancer

High blood calcium levels are called hypercalcaemia. This is pronounced high-per-kal-see-mee-a. This usually happens in advanced cancer and is rare in people with earlier stages of cancer.

Why people with cancer can have high calcium

The cancer makes calcium leak out into the bloodstream from your bones, so the level in the blood gets too high. The cancer might also affect the amount of calcium that your kidneys are able to get rid of. Damaged areas of bone can release calcium into your bloodstream if you have bone secondaries. 

Dehydration from being sick a lot or having diarrhoea might also increase calcium levels. It is very important that you do something about this. High blood calcium can make you more and more drowsy until you are sleeping nearly all the time. You might go into a coma and eventually die if it is not treated. 

The types of cancers that are most commonly associated with high blood calcium are:

  • myeloma – nearly half of all people with myeloma have this at some stage
  • breast cancer
  • squamous cell lung cancer
  • kidney cancer
  • head and neck cancers
  • prostate cancer

Although less common, high blood calcium can happen in other types of cancer.


It is not always easy for a doctor to spot that you have high calcium. You might not have any definite symptoms. You might just feel a bit unwell or very tired.

The severity of your symptoms doesn’t always match up to the calcium level in your blood. People with a slightly high calcium level can have very severe symptoms and people with a very high calcium level might only have mild symptoms.

Many of the symptoms are common in advanced cancer, even in people who do not have high blood calcium levels.

All this can make it difficult for your doctor to spot high calcium. But the first signs might be:

  • extreme tiredness (fatigue) and lethargy
  • feeling weak
  • not wanting to eat much
  • constipation
  • loss of concentration and interest in doing things
  • mild confusion

Untreated high calcium symptoms might become much worse and can include:

  • feeling and being sick
  • drowsiness
  • passing large amounts of urine
  • feeling very thirsty
  • dehydration
  • confusion
  • agitation
  • muscle spasms
  • tremors
  • bone pain and weakness
  • irregular heart beat
  • difficulty thinking and speaking clearly
  • coma and finally death, if not treated

Because calcium plays a role in the normal working of the brain and spinal cord, if you have severely high calcium levels you might also:

  • have fits (seizures)
  • be unable to coordinate muscle movement, which can affect walking, talking and eating
  • have changes in personality
  • have hallucinations

Your specialist will treat you if you have high calcium levels. It can be a life threatening condition if it is not treated. You might have to spend a day or 2 in hospital to get your calcium levels down.

Last reviewed: 
25 May 2016
  • Cancer and its management (7th edition)
    J Tobias and D Hochhauser
    Wiley-Blackwell, 2015

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