MAGNESIUM supplements face scrutiny as new evidence shows no meaningful protection against tachyarrhythmias among critically ill patients. The findings suggest that routine correction of modestly low serum magnesium levels may not deliver the expected cardiac benefits.
Long Standing Beliefs About Magnesium Supplements
For decades, clinicians have administered magnesium supplements to intensive care patients with mild to moderate hypomagnesaemia, based on concerns about atrial fibrillation and other tachyarrhythmias. This practice has persisted despite limited causal evidence and has often been influenced by perceived risk rather than clear outcome data. The current investigation aimed to address this gap by determining whether magnesium supplements genuinely reduce arrhythmia risk when given at commonly used thresholds.
Large Scale ICU Trial Challenges Assumptions
The study analysed 478901 twenty-four-hour treatment windows from 171727 admissions across 93 ICUs in the United States and Europe between 2003 and 2022. A fuzzy regression discontinuity design was applied to patients just above and just below institutional treatment cutoffs, which ranged from 1.6 mg per dL to 2.0 mg per dL. Among the cohort, 72767 patients were female and 98960 were male, with a mean age of 63 years. Magnesium supplementation was not associated with a statistically significant reduction in ventricular or supraventricular tachyarrhythmias, showing a risk difference of 0.1 percent with a 95 percent confidence interval from minus 4.2 to 6.9. There were also no meaningful associations with hypotension, which showed a risk difference of 1.2 percent with a 95 percent confidence interval from minus 0.9 to 17.7, or with death, which showed a risk difference of 1.4 percent with a 95 percent confidence interval from minus 0.6 to 5.3. The results were consistent across all evaluated cutoffs.
Implications for Clinical Practice
These findings suggest that routine magnesium supplements at standard doses may not be warranted for patients whose serum magnesium values fall near the commonly applied thresholds. Clinicians may need to reconsider automatic supplementation and focus on truly hypomagnesaemic patients while awaiting further targeted research that identifies those who stand to benefit most.
Reference
Goulden R et al. Magnesium supplementation and tachyarrhythmias: a nonrandomized clinical trial. JAMA Intern Med. 2025;DOI:10.1001/jamainternmed.2025.6572.
