High calcium in people with cancer

High blood calcium levels are called hypercalcaemia. It’s 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 can make 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 cancer that has spread to the bone.

Dehydration from being sick a lot or having diarrhoea might also increase calcium levels. It is very important that you get help from your doctor if this happens to you. High blood calcium can make you more and more drowsy until you are sleeping nearly all the time. You might go into a coma if it’s not treated.

Which cancers might cause high calcium?

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

  • myeloma – about 30 in 100 people (about 30%) have high calcium when they are first diagnosed
  • breast cancer
  • lung cancer
  • kidney cancer
  • 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.

How serious your symptoms are 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.

First symptoms

It can be 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
  • low mood
  • irritability

Untreated high calcium symptoms

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

  • feeling and being sick
  • drowsiness
  • passing large amounts of urine
  • feeling very thirsty or dehydrated
  • confusion or agitation
  • muscle spasms
  • tremors
  • bone pain and weakness
  • irregular heart beat
  • difficulty thinking and speaking clearly

It might also lead to coma and eventually death if not treated.

Brain and spinal cord symptoms

Calcium plays a role in the normal working of the brain and spinal cord. So 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


Your specialist will treat you if you have high calcium levels. You might have to have treatment in hospital.

Last reviewed: 
21 Nov 2018
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