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Test ID: Magnesium
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Magnesium
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Useful For
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Assessment of neuromuscular disorders. It also aids in the evaluation of preeclampsia for pregnant women.
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Method name and description
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Colorimetric endpoint method
In alkaline solution, magnesium forms a purple complex with xylidyl blue, diazonium salt. The magnesium concentration is measured photometrically via the decrease in the xylidyl blue absorbance.
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Clinical information
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Magnesium along with potassium is a major intracellular cation. Approximately 69 % of magnesium ions are stored in bone. The rest are part of the intermediary metabolism, about 70 % being present in free form while the other 30 % is bound to proteins (especially albumin), citrates, phosphate, and other complex formers. Regulation takes place mainly via the kidneys, especially via the ascending loop of Henle.
This assay is used for diagnosing and monitoring hypomagnesemia (magnesium deficiency) and hypermagnesemia (magnesium excess). Numerous studies have shown a correlation between magnesium deficiency and changes in calcium, potassium and phosphate homeostasis which 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. Hypermagnesemia is found in acute and chronic renal failure, magnesium excess, and magnesium release from the intracellular space.
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Specimen type / Specimen volume / Specimen container
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Specimen type: Serum, Plasma
Minimum volume of sample: 1 mL
Serum: Plain tube (red or yellow top)
Plasma: Li‑heparin tube
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Collection instructions / Special Precautions / Timing of collection
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Collect blood by standard venipuncture techniques as per specimen requirements. When processing samples in primary tubes (sample collection systems), follow the instructions of the tube manufacturer.
Chelating anticoagulants such as EDTA, fluoride and oxalate must be avoided.
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Storage and transport instructions
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Storage: 7 days at 15– 25°C
7 days at 2 – 8°C;
1 year at ‑20 °C (± 5 °C)
Transport: 2-25°C
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Specimen Rejection Criteria
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Grossly hemolyzed, icteric and lipemic, wrong collection container, insufficient sample.
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Biological reference intervals and clinical decision values
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Patient Sex
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Age Range
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Range (mmol/L)
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Female/Male
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0 Min
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To
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28 days
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0.6 – 1.0
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Female/Male
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28 days
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To
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150 years
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0.7 – 1.0
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Turnaround time / Days and times test performed / Specimen retention time
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Daily (24/7)
Turn-around time:
STAT: 1 hour
Routine: One working day
Specimen retention: 4 days
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