Magnesium

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Also known as: Mg

At a Glance

Why Get Tested?

To evaluate the concentration of magnesium in your blood and to help determine the cause of abnormal calcium and/or potassium levels

When to Get Tested?

If you have symptoms (such as weakness, irritability, cardiac arrhythmia, nausea, and/or diarrhoea) that may be due to too much or too little magnesium or if you have abnormal calcium or potassium levels

Sample Required?

A blood sample taken from a vein in your arm

Test Preparation Needed?

None

The Test Sample

What is being tested?

This test measures the amount of magnesium in your blood. Normally, only a very small amount (about 1%) of the total magnesium found in the body is present in the blood.

Magnesium is a mineral that is found in every cell of your body. It is vital to energy production, muscle contraction, nerve function, and maintenance of strong bones. About half of the body’s magnesium is combined with calcium and phosphorus to form bone.

A wide variety of foods contain small amounts of magnesium, especially green vegetables such as spinach, and most magnesium in the body comes from dietary sources. The body maintains magnesium levels in its blood, cells, and bone by regulating how much it absorbs from the intestines and by how much it excretes or conserves in the kidneys.

How is the sample collected for testing?

A blood sample is obtained by inserting a needle into a vein in the arm.

NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.

Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed.

The Test

Common Questions

Ask a Laboratory Scientist

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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.