Special Precautions/Comments:

Additional Information:

Magnesium is the second most abundant intracellular cation and an important cofactor in >300 enzymatic reactions within cells. As such, magnesium has a variety of functions including energy metabolism, cell replication, protein synthesis, oxidative phosphorylation and neuromuscular excitability.  The majority of magnesium is found intracellularly (45%) or within the bone (55%), whereas approximately 1% is in the serum.  

Magnesium facilitates the secretion of parathyroid hormone (PTH) and therefore measurement is useful in the investigation of hypoparathyroidism. Due to its role in K+ homeostasis, measurement is also useful in refractory hypokalaemia. 

Low serum magnesium (hypomagnesaemia) can be caused by inadequate intake, alcoholism, malabsorption, osmotic diuresis (due to diabetes) and renal tubular dysfunction. Hypomagnesaemia can also arise due to a shift of magnesium from the serum into cells, such as in refeeding syndrome or hungry bone syndrome. Some drugs, particularly proton pump inhibitors (PPIs), may also result in a low serum magnesium. 

Hypermagnesaemia can be caused by renal failure, increased intake (usually from an iatrogenic cause) or a shift from the cells into the serum, such as in acute acidosis or tumour lysis syndrome.