Abnormal levels of magnesium are most frequently seen in conditions or diseases that cause impaired or excessive excretion of magnesium by the kidneys or that cause poor absorption in the intestines. Magnesium levels may be checked as part of an evaluation of the severity of kidney problems or of uncontrolled diabetes and may help help in the diagnosis and monitoring of gastrointestinal disorders, sometimes characterised by prolonged diarrhoea.
Since a low magnesium level can, over time, cause persistently low calcium and potassium levels, it may be checked to help diagnose problems with calcium, potassium, phosphorus, and/or parathyroid hormone (involved with calcium regulation).
Magnesium levels may be measured frequently to monitor the response to oral or intravenous (IV) magnesium supplements and may be used, along with calcium and phosphorus testing, to monitor calcium supplementation. Magnesium supplementation is also used in the treatment of pre-eclampsia in pregnancy, where supplementation is given intravenously and blood levels are then checked to ensure adequacy of treatment.
Magnesium testing may be requested as a follow-up to persistently low levels of calcium and potassium. It may also be requested if you have symptoms of an abnormally low magnesium level such as muscle weakness, twitching, cramping, confusion, cardiac arrhythmias, and seizures.
Although dietary deficiencies of magnesium are rare, your doctor may request a magnesium blood test to check for a deficiency as part of an evaluation of malabsorption, malnutrition, diarrhoea, or alcoholism. If you are taking certain drugs that can cause the kidneys to excrete magnesium, testing may also be performed. If magnesium and/or calcium supplementation is necessary, then the level of magnesium in the blood is likely to be checked at intervals to monitor the effectiveness of treatment.
If you have a kidney disorder or uncontrolled diabetes, your doctor may request a blood test to measure magnesium to help monitor kidney function and to make sure that you are not excreting or retaining excessive amounts of magnesium.
Low levels of magnesium (hypomagnesaemia) in your blood may mean that you are: 1) not getting enough magnesium in your diet; 2) your intestines are not absorbing enough magnesium; or 3) your kidneys are excreting too much magnesium. Deficiencies may be due to:
Low dietary intake (seen in the elderly, malnourished, and with alcoholism)
Gastrointestinal disorders (such as Crohn’s disease)
This article was last reviewed on 18 July 2012. | This article was last modified on 24 June 2016.
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