Magnesium test: what it’s for, procedure & results explained

By HealthEngine

Last updated: 19 January 2018

What is magnesium?

Magnesium (Mg) is an important element involved in cellular processes.

The correlation between magnesium stores and blood levels is not clear, but both may be decreased in malnourished individuals and those taking diuretics – ‘water tablets’.

When would you need a magnesium test?

Low magnesium in the bloodstream is known as hypomagnesaemia.

This is a rare condition, but may be more common in malnourished people, especially alcoholics, and people taking diuretics, or in some rare kidney conditions.

Lack of magnesium can have effects on the nervous system, muscles, and the cardiovascular system.

Symptoms are quite non-specific, but may include:

  • Weakness
  • Muscle cramps
  • Palpitations (awareness of a rapid heartbeat)

How is a magnesium test performed?

A magnesium test is a blood test and requires a few millilitres of blood from a vein.

Magnesium test results explained

The level of magnesium in the blood is only a small proportion of the body stores of magnesium.

When body stores are low, healthy kidneys will conserve magnesium, before the blood level drops, and measurement of the 24-hour urine magnesium level may be helpful.

If the blood level is low, the total body magnesium is probably low, but blood level measurements are affected by the quantity of proteins in the blood, and how strongly magnesium is bound to these proteins.

Related specialists

Related tests

Also known as

  • Mg
  • Serum magnesium



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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.