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Electrolytes
Magnesium (Mg)
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This is the date the draft was written, not a medical review date.
Magnesium is mainly intracellular and bone-bound; serum levels (about 1 % of the body store) are an imperfect indicator of total body magnesium.
Reference interval
| Conventional (mg/dL) | SI (mmol/L) | |
|---|---|---|
| Adults | 1.7–2.2 mg/dL | 0.7–0.91 mmol/L |
Specimen: Serum · Conventional × 0.4114 = SI
Causes of high values
Hypermagnesaemia is uncommon: kidney failure, magnesium-containing antacids or laxatives, and magnesium sulphate therapy.
Causes of low values
Hypomagnesaemia: diuretics, proton pump inhibitors, alcohol use, diarrhoea and malabsorption, aminoglycosides, cisplatin, diabetes and refeeding. It causes refractory hypokalaemia and hypocalcaemia and can predispose to arrhythmias.
Pre-analytical and method notes
Reference limits vary by laboratory (commonly 0.7-1.0 mmol/L). Haemolysis falsely raises serum magnesium; a normal serum value does not exclude intracellular depletion. 1 mmol/L equals 2.43 mg/dL, or 2 mEq/L.
References
- Rifai N, Horvath AR, Wittwer CT. Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. Elsevier, 6th edition (2018) — Tier 3 (textbook)
- Loscalzo J, et al.. Harrison's Principles of Internal Medicine. McGraw-Hill, 21st edition (2022) — Tier 3 (textbook)
- McPherson RA, Pincus MR. Henry's Clinical Diagnosis and Management by Laboratory Methods. Elsevier — Tier 3 (textbook)
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