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Unit Code 460084:
Magnesium, Serum

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Useful For

Magnesium levels may be used to monitor preeclampsia patients

being treated with magnesium sulfate, although in most cases

monitoring clinical signs (respiratory rate and dep tendon reflexes) is

adequate and blood magnesium levels are not required.

Clinical Information

Magnesium, along with potassium, is a major intracellular cation.

Magnesium is a cofactor of many enzyme systems. All

ATP-dependent enzymatic reactions require magnesium as a

cofactor. Approximately 70% of magnesium ions are stored in

bone. The remainder is involved in intermediary metabolic

processes; about 70% is present in free form, while the other 30%

is bound to proteins (especially albumin), citrates, phosphate,

and other complex forms. The serum magnesium level is kept

constant within very narrow limits. Regulation takes place mainly

via the kidneys, primarily via the ascending loop of Henle.

 

Conditions that interfere with glomerular filtation result in retention

of magnesium and hence elevation of serum concentrations.

Hypermagnesemia is found in acute and chronic renal failure,

magnesium overload, and magnesium release from the

intracellular space. Mild-to-moderate hypermagnesemia may

prolong atrioventricular conduction time. Magnesium toxicity may

result in central nervous system (CNS) depression, cardiac

arrest, and respiratory arrest.

 

Numerous studies have shown a correlation between

magnesium deficiency and changes in calcium, potassium,

and phosphate homeostasis that are associated with cardiac

disorders such as ventricular arrhythmias that cannot be

treated by conventional therapy, increased sensitivity to

digoxin, coronary artery spasms, and sudden death. Additional

concurrent symptoms include neuromuscular and neuropsychiatric

disorders. Conditions that have been associated with

hypomagnesemia include chronic alcoholism, childhood

malnutrition, lactation, malabsorption, acute pancreatitis,

hypothyroidism, chronic glomerulonephritis, aldosteronism,

and prolonged intravenous feeding.

Reference Values

0-15 years: Not established

> or =16 years: 1.8-2.5 mg/dL

Interpretation

Symptoms of magnesium deficiency do not typically appear until

levels are < or =1.0 mg/dL. Levels > or =10 mg/dL may be

life-threatening.

 

Normal serum magnesium levels range from 1.7-2.1 mg/dL.

Cautions

Serum or plasma magnesium concentration provides only an

approximate guide to the presence or absence of magnesium

deficiency. Hypomagnesemia reliably indicates magnesium deficiency,

but its absence does not exclude significant magnesium depletion.

The concentration of magnesium in serum has not been shown to

correlate with any other tissue pools of magnesium except

interstitial fluid.

Special Instructions and Forms

• Metals Analysis - Collection and Transport 

Clinical Reference

1.   Tietz Textbook of Clinical Chemistry. 4th edition. Edited by  

      CA Burtis, ER Ashwood, and DE Bruns. Philadelphia,       WB Saunders Company, 49:1893-1912, 2006  

2.   Ryan MF:  The role of magnesium in clinical biochemistry: an

      overview. Ann Clin Biochem 1991;28:19

Key