Calcium blood test: what it is, what it’s for & results explained

What is calcium?

Calcium (Ca) is an ion that is essential for many body processes, including nerve conduction, muscle contraction, and bone metabolism.

What is a calcium test?

A calcium test (or serum calcium) is usually performed to diagnose osteoporosis (thinning of the bones) but it is helpful to exclude other metabolic bone conditions.

Calcium and phosphate tests are often requested together as part of a metabolic bone profile.

When would you need a calcium test?

The symptoms of hypercalcaemia (high calcium level in the blood) can be quite non-specific and include the so-called ‘bones, groans and kidney stones’. Namely:

  • Bony pain due to a process within the bones causing a high calcium level (bones)
  • Abdominal pain which may be diffuse (groans)
  • Or localsied to the kidney area as in kidney stones (renal colic, ureteric colic)

Hypercalcaemia may also cause thirst, lethargy, and very rarely, an altered conscious state.

Patients with some haematological cancers, or cancers which arise in bones or spread to bones, are more prone to this condition.

Low serum calcium (hypocalcaemia) is quite rare and is almost confined to people who have had their parathyroid glands removed or damaged by surgery.

Hypocalcaemia causes painful muscle spasms, known as tetany – not to confused with tetanus, an infectious disease caused by the bacterium Clostridium tetani.

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How is a calcium test is performed?

Calcium levels are performed on a small sample of blood (a few millilitres) from a vein or an artery.

Calcium blood test results explained

Because calcium is transported in the blood mostly bound to the protein Albumin, a serum calcium level needs to be taken in context of the Albumin level, and there are various formulas for calculating this ‘corrected calcium’.

In uncommon circumstances, an arterial blood sample may have to be taken to check the ionised calcium level, which is the biochemically active fraction of calcium not bound to Albumin.

Also Known As

  • Serum calcium

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This article is for informational purposes only and should not be taken as medical advice. If in doubt, HealthEngine recommends consulting with a registered health practitioner.