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Low magnesium is a serum plasma level of less than 0.7 mmol/ L or < 1.46 mg/ dL.


Symptoms most likely when levels < 0.5 mmol / L. Symptomatic hypomagnesemia is often associated with hypocalcemia and hypokalaemia. 2nd most abundant intracellular cation -imp for cellular function , nerve conduction and other needs. Emergency – usually IV replacement is needed.


anorexia nausea / vomiting CNS – confusion , apathy , depression , hallucinations , agitation weakness / lethargy paraesthesia tetany / paresthesia / tremor / muscle fasciculations / seizures cardiac arrhythmias : digitalis toxicity may be enhanced , non -specific ECG changes , tachycardia , hypertension other electrolyte abnormalities as low Ca , K , hypoparathyroidism.


Symptoms can be non- specific and attributed to low calcium and potassium Work up – Ca , ph , Us & Es , glucose , ECG 24 hr urinary Mg excretion.


Symptoms – Gastrointestinal diarrhoea , vomiting , stoma or fistula output malabsorption medications ( e,g PPIs ) GI fistulae / gastric bypass malnutrition dietary deficiency.


Metabolic-chronic alcoholism uncontrolled diabetes ketoacidosis parathyroid disorders low Vit D acute pancreatitis re-feeding syndrome acidosis.


Others -renal losses blood transfusion drugs ( e,g loop & thiazide diuretics , theophylline , 
digoxin ) genetic causes ( Gitelman , Barters ) critical illness ( TPN )


green leafy vegetables 
( e.g spinach ) dairy foods nuts wholegrain bread fish meat unrefined grains.


mild asymptomatic – look for causes & offer dietary advice
( treatment not always required ) replace if symptomatic take into account kidney function / severity of symptoms moderate – oral replacement if asymptomatic & IV replacement if symptomatic oral magnesium can be given orally up to 24 mmol Mg2+ daily in divided doses monitoring depends upon clinical circumstances but if replacing orally consider checking Mg level in 5- 7 days address any underlying Ca / K+ abnormalities if on PPIs-> stop -> replace with H2 blocker -> check Mg 2wk if eGFR < 30 -either do not replace or consider significantly reduced dose ( renally excreted ).


Magnesium aspartate sachets -1 sachet which is 10 mmol ( 243 mg ) BD dissolve in 50-200 ml of water diarrhoea ( or increased output in stoma pts ) -adv to take with food


Magnesium glycerophosphate chewable tablets -2 x 4 tablets TDS
97mg / tablet.


  1. Gragossian A, Bashir K, Friede R. Hypomagnesemia. [Updated 2022 May 15]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from:
  2. Management of Hypomagnesaemia in adults in primary care
  3. Guideline for the Management of Hypomagnesaemia in Adults
    This guideline is only for use in hypomagnesaemia, not for other therapeutic indications.
  4. Hypomagnesaemia – a guide for GPs


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