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Hypomagnesemia

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.

REFERENCES

  1. Gragossian A, Bashir K, Friede R. Hypomagnesemia. [Updated 2022 May 15]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK500003/
  2. Management of Hypomagnesaemia in adults in primary care https://www.shropshiretelfordandwrekinccg.nhs.uk/wp-content/uploads/management-of-hypomagnesaemia-in-adults-in-primary-care-v2.pdf
  3. Guideline for the Management of Hypomagnesaemia in Adults
    This guideline is only for use in hypomagnesaemia, not for other therapeutic indications. https://www.gloshospitals.nhs.uk/media/documents/Hypomagnesaemia_jcPg0oV.pdf
  4. Hypomagnesaemia – a guide for GPs https://www.ruh.nhs.uk/pathology/documents/clinical_guidelines/PATH-021_Hypomagnesaemia_Guideline.pdf

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