Blood-tests Explained


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This website is intended to assist with patient education and should not be used as a diagnostic, treatment or prescription service, forum or platform. Always consult your own healthcare practitioner for a more personalised and detailed opinion

Magnesium


At a Glance

Why Get Tested?

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

When to Get Tested?

When you have symptoms such as weakness, irritability, cardiac arrhythmia, nausea, and/or diarrhea that may be due to too much or too little magnesium; when you have abnormal calcium or potassium levels

Sample Required?

A blood sample drawn from a vein in your arm; sometimes a timed urine collection that most often requires a 24-hour sample

Test Preparation Needed?

For a blood sample, overnight fasting may be required; follow any instructions that you are given.

The Test Sample

What is being tested?

Magnesium is a mineral that is vital for energy production, muscle contraction, nerve function, and the maintenance of strong bones. It comes into the body through the diet and is absorbed by the small intestine and colon. Magnesium is stored in the bones, cells, and tissues. Normally, only about 1% of total body magnesium is present in the blood and this makes it difficult to get an accurate measurement of total magnesium content from blood tests alone. However, this test is still useful for evaluating a person's magnesium status.

A wide variety of foods contain small amounts of magnesium, especially green vegetables such as spinach, as well as whole grains and nuts. Foods that have dietary fiber are usually also sources of magnesium. The body maintains its magnesium level by regulating how much it absorbs andhow much it excretes or conserves in the kidneys.

Magnesium deficiencies (hypomagnesemia) may be seen with malnutrition, conditions that cause malabsorption, and with excess loss of magnesium by the kidneys.Magnesium excess (hypermagnesemia) may be seen with the ingestion of antacids that contain magnesium and with decreased ability of the kidneys to excrete magnesium.

Someone with mild to moderate magnesium deficiency may have no or few nonspecific symptoms. Persistent or severe deficiencies can cause nausea, loss of appetite, fatigue, confusion, muscle cramps, seizures, changes in heart rate, and numbness or tingling. They can also affect calcium metabolism and exacerbate calcium deficiencies. Symptoms of excess magnesium can be similar to those of deficiency and include nausea, muscle weakness, loss of appetite, and an irregular heart rate.

How is the sample collected for testing?

A blood sample is obtained by inserting a needle into a vein in the arm. Sometimes a timed urine sample is obtained, such as a 24-hour collection.

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

Overnight fasting may be required prior to having a blood sample drawn; follow any instructions that you are given.

The Test