What is a calcium blood test?

A calcium blood test measures how much calcium is in your blood. It can help your doctor check for problems in your bones, kidneys or parathyroid glands.

There are 3 types of calcium blood tests:

• total calcium test — measures both free calcium (which your body can use) and bound calcium (attached to proteins and stored). It is the most common test.
• corrected calcium test — takes the total calcium and adjusts it for changes in a protein called albumin, giving a slightly more accurate total calcium score
• ionised calcium test — measures only the free calcium in your blood. This is important if the balance between stored and usable calcium is not normal.

What is calcium and why is it important?

Calcium is a mineral that helps build strong bones and teeth. Most calcium in your body is stored in your bones.

Calcium is also important for muscle movement, blood clotting and sending signals through your nervous system.

You lose some calcium every day in your urine. Your doctor might also test your urine (wee) to find out how much calcium your kidneys are removing.

When is a blood glucose test used?

A calcium blood test is done to help diagnose, screen or monitor health conditions that affect calcium levels in your blood.

Your doctor may refer you for this test if you:

• have symptoms of high calcium levels (hypercalcaemia)
• have symptoms of low calcium levels (hypocalcaemia)
• have a health condition that affects the balance of calcium in your body

High calcium levels

Too much calcium in your blood may cause symptoms, such as:

• tiredness
• weakness
• anxiety
• headaches
• frequent urination
• constipation
• nausea, vomiting or pain in your abdomen (tummy)

Low calcium levels

Too little calcium in your blood may cause symptoms, such as:

• numbness or tingling, especially around your mouth, hands and feet
• muscle weakness, spasms or cramps
• confusion or memory loss
• depression
• seizures (in severe situations)

Routine testing

Your doctor may refer you for a calcium blood test as part of routine monitoring if you have or are at risk of:

• kidney disease or kidney stones
• bone problems, including osteoporosis
• parathyroid problems, such as hyperparathyroidism
• some types of cancer
• gastrointestinal illness that affect calcium absorption
• poor nutrition or vitamin D deficiency

Your doctor may also recommend checking your calcium levels if you take medicines or supplements affecting calcium levels, such as diuretic medicines, calcium or vitamin D supplements.

Where can I get a calcium blood test?

You usually need to go to a pathology collection centre. Your doctor will recommend one near you.

Sometimes, your doctor will collect blood for testing in their clinic. Blood tests are also routinely done in hospitals.

How do I prepare for a calcium blood test?

No special preparation is needed for a calcium blood test. However, it is a good idea to ask your doctor if you should stop taking certain medicines, such as diuretics or supplements, before the test.

However, if you are having other blood tests done at the same time, you may need to prepare. Check with your doctor or the pathology collection centre if there is anything you need to do before your blood test.

What happens during a calcium blood test?

A health professional will take a sample of blood, usually from a vein in your arm. The blood will then be sent to a laboratory for testing.

What do my calcium blood test results mean?

Your calcium blood test shows if your calcium levels are normal, too high or too low.

• Normal calcium — if your results are within the reference range, it usually means your body is maintaining a healthy calcium level.
• High calcium (hypercalcaemia) — can be caused by an overactive parathyroid gland, too much vitamin D and some illnesses, such as cancer.
• Low calcium (hypocalcaemia) — may happen due to low vitamin D levels, kidney problems or not enough albumin (a protein) in your blood.

If your calcium levels are too high or too low, your doctor may suggest further tests to find out why and to help guide treatment.

Resources and support

• Read healthdirect's 'Guide to blood testing' to learn more about blood tests.
• Pathology Tests Explained also has more information on calcium tests and other blood tests.
• Healthy Bones Australia provides information on why calcium is important for bone health.

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.

Other languages

NSW Government offers translated information in languages other than English on topics, such as:

• how your calcium needs change as you get older
• why calcium is important for healthy bones