Magnesium

Magnesium has been called the 'forgotten cation' of medicine. There's no need for this to be the case now that it can be easily measured in the lab. You just need to remember to ask for it.

Magnesium is pretty important to us. Over 300 enzymes depend on it as a co-factor!

Magnesium in the diet (eg from green vegetables) is absorbed from the gut. The regulation of magnesium homeostasis is performed mainly by the kidneys. The plasma magnesium concentration is a major determinant of urinary magnesium excretion. Magnesium in the body is stored in bone and muscle.

Magnesium in the plasma is bound in a similar kind of way to calcium and so it exists bound to protein, complexed to anions and free. 'Adjustment' for a low albumin is required in the same way as calcium  but the factor is less (add 0.1 mmol/l for a 20g/l drop in albumin for magnesium compared to 0.4 mmol/l for calcium).

(Serum magnesium = 0.7-1.0 mmol/l)