Magnesium (Mg2+) plays a critical role in numerous metabolic function in our body. Normal levels of both intra- and extra cellular magnesium are necessary for correct cellular processes. The specific clinical conditions in which Mg2+ deficiency has been implicated to play a pathophysiological role include depression, ischaemic heart disease, arrhythmias, preeclampsia, asthma, intradialytic hypotension or critical illness. Correct administration of magnesium can eliminate perioperative pain and muscle spasms, keep blood flowing smoothly, and prevent platelet stickiness. Although magnesium sulphate is now widely used to prevent or control eclamptic convulsions, there is no consensus on the optimal dosage and concentration of magnesium sulphate for the management of eclamptic seizures. Owing to its bronchodilating and anti-inflammatory effects, Mg2+ is an encouraging adjuvant therapy for paediatric patients, although its use is often limited to patients who do not respond to conventional treatment. Studies have also suggested that magnesium might be useful as an agent to control the rigidity and spasms of severe tetanus or for the enhancement of neuromuscular blockade during anaesthesia, but its actual efficacy as an anticonvulsant or an adjuvant to analgesics and anaesthetics to induce and maintain anaesthesia remains unclear. Moreover, a negative correlation has been shown between intradialytic changes of the serum magnesium and hypotensive episodes during dialysis sessions. Low Mg2+ haemodialysis solution resulted in both hypomagnesaemia and hypocalcaemia. Mg2+ compounds are now becoming recognized as safe, effective and cost-efficient alternatives to other phosphorus binders, with a significant added benefit of substantially reducing the risk and impact of cardiovascular diseases. It seems that magnesium is underused in clinical conditions, considering its therapeutic capacity. On the other hand, numerous studies have found conflicting results, questioning the implicit efficacy of magnesium in several clinical conditions.