Calcium blood test
Key facts
- Calcium blood tests are used to find out if your blood calcium is at normal levels.
- There are many reasons why you might need a calcium blood test.
- A calcium blood test doesn't tell you about the calcium in your bones.
- Your doctor will explain your test results.
What is being tested?
Almost all the calcium in your body is found in your bones. The rest of it is found in your blood. This test is to find out if your blood calcium is at normal levels.
Calcium is important because it is needed for strong bones. Your muscles, nerves and heart also need calcium to work properly. Calcium is needed for your blood to clot.
You lose some calcium every day in your urine. Your doctor might also test your urine (pee) to find out how much calcium your kidneys are removing.
Why would I need this test?
There are many reasons why you might need a calcium blood test. Blood tests help your doctor:
- to make a diagnosis
- screen for illness
- monitor treatments
Your doctor might suspect you have too much calcium in your blood if you are:
- tired
- weak
- thirsty
- have lost your appetite
- need to urinate a lot
- are constipated
- have pain in your abdomen
They might suspect you have too little calcium in your blood if you get:
- numbness around your mouth
- numbness in your hands and feet
- muscle spasms
A blood test for calcium can be part of routine testing if you have or might have:
- kidney disease
- kidney stones
- bone problems or osteoporosis
- thyroid problems or hyperparathyroidism
- intestinal illness
- some types of cancer
- poor nutrition
You might need repeated tests for calcium if:
- you have kidney disease
- you have had a kidney transplant
- you are taking calcium or vitamin D supplements
- you have some types of cancer, especially those that affect the bones
How should I prepare for the test?
Your doctor might ask you to stop taking medicines such as antacids, diuretics and vitamin D supplements. These may contain calcium or affect how much calcium there is in your blood.
Otherwise, there is no special preparation needed for a calcium blood test.
However, if you are having other blood tests done there may be special preparations instructions.
It's best to check with your doctor or the pathology collection centre. Ask them if there is anything you need to do before having your blood test.
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What does the result mean?
A calcium test provides information about how much calcium is in your blood. It doesn't tell you about the calcium in your bones. This test is usually looked at with other results and tests.
You need to talk to your doctor to understand the results of your test, and to find out what comes next.
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Resources and support
To learn more about blood tests you can read healthdirect's Guide to blood testing.
Pathology Tests Explained also has more information on blood tests including calcium tests.
You can also call the healthdirect helpline on 1800 022 222 (known as NURSE-ON-CALL in Victoria). A registered nurse is available 24 hours a day, 7 days a week.
Learn more here about the development and quality assurance of healthdirect content.
Last reviewed: October 2023
