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Magnesium (blood)

Category Biochemistry
Test background

Hypomagnesaemia (often associated with hypokalaemia and/or hypocalcaemia) may reflect inadequate dietary intake (eg. malnutrition, alcoholism, etc.), inadequate absorption by the GI tract (eg. Crohn’s, diarrhoea) or excessive renal excretion (eg. secondary to diabetes mellitus, long-term use of diuretics). In contrast, increased serum magnesium typically reflects kidney failure, hyperparathyroidism, Addison’s disease or is due to the administration of magnesium-containing compounds, eg. laxatives, antacids and magnesium sulphate (used in the prophylaxis of eclampsia).

Clinical Indications

Investigation of hypocalcaemia and/or hypokalaemia
Monitoring/diagnosis of electrolyte and acid/base disturbance
Monitoring of pre-eclampsia

Reference range
Over 1 month old 0.7-1.0 mmol/L
Less than 1 month 0.6-1.0 mmol/L



Sample & container required SST (gold top) or Red top
Sample volume 0.5 mL
Turnaround time 1 day