Mineral for muscle, nerve, and heart rhythm function.
What it is
Serum magnesium in mmol/L. Blood levels poorly reflect total body stores but still guide clinical decisions when abnormal.
Serum magnesium is a small, tightly controlled pool; most magnesium is intracellular or in bone. Low serum levels are still clinically actionable. Reported in mmol/L.
Why it matters
Low magnesium may accompany diarrhoea, alcohol use, proton-pump inhibitors, or poor intake. Symptoms and ECG risk are clinical decisions, do not megadose magnesium blindly.
This guide is educational only and cannot diagnose you. Discuss results, especially anything outside your laboratory’s reference interval, or that does not match how you feel, with a GP or other appropriately qualified clinician.
How it affects the body
Magnesium stabilises neuromuscular excitability and participates in hundreds of enzymatic reactions including ATP handling.
Magnesium stabilises ATP, modulates NMDA/calcium channels, and supports muscle relaxation after contraction. Deficiency increases neuromuscular excitability and arrhythmia risk in vulnerable patients.
For athletes
Sweaty athletes often take magnesium for cramps; evidence is mixed. Correct documented deficiency under guidance; cramps have many causes (load, sodium, fatigue).
Evidence for magnesium fixing all cramps is weak; documented deficiency should be corrected under guidance. Review PPIs, diarrhoea, and alcohol with your clinician.
