Magnesium Citrate is NOT Associated with Causing Atrial Fibrillation
Magnesium citrate does not cause atrial fibrillation; in fact, low magnesium levels are associated with increased AF risk, and magnesium supplementation may help prevent and treat AF.
The Protective Role of Magnesium
The evidence consistently demonstrates an inverse relationship between magnesium levels and atrial fibrillation risk:
Low Magnesium Increases AF Risk
Lower serum magnesium is associated with higher AF incidence. In the ARIC study of 14,290 participants, those in the lowest quintile of serum magnesium had a 34% increased risk of developing AF compared to the middle quintile (HR 1.34,95% CI 1.16-1.54) 1.
The Framingham Heart Study confirmed this finding: individuals in the lowest quartile of serum magnesium (≤1.77 mg/dL) had approximately 50% higher risk of developing AF compared to those in the highest quartile (adjusted HR 1.52,95% CI 1.00-2.31) 2.
In critically ill ICU patients, hypomagnesemia at AF onset was independently associated with a 2.5-fold increased risk of new-onset AF (OR 2.52,95% CI 1.19-5.36) 3.
Magnesium Supplementation May Prevent and Treat AF
Protocolized magnesium supplementation in ICU patients showed a 1.6% absolute risk reduction in 24-hour AF/flutter incidence (91% probability of benefit) in a large multicenter study of 4,198 critically ill patients 4.
For acute AF management, IV magnesium in addition to standard therapy improves both rate control (OR 1.87,95% CI 1.13-3.11) and rhythm control (OR 1.45,95% CI 1.04-2.03) in non-postoperative patients 5.
Guideline Support for Magnesium Monitoring
The 2023 ACC/AHA/ACCP/HRS AF Guidelines emphasize the importance of magnesium monitoring in AF management 6:
- Serum magnesium concentrations should be checked and corrected before initiating antiarrhythmic drugs like ibutilide to minimize risk of torsades de pointes
- Regular monitoring of magnesium is recommended for patients on dofetilide and sotalol (every 3-6 months)
- Hypomagnesemia correction is specifically recommended before antiarrhythmic drug infusions
Clinical Implications
The concern should be hypomagnesemia (low magnesium), not magnesium supplementation:
- Magnesium citrate 7 is a commonly used oral magnesium supplement and laxative
- The FDA labeling warns about use in kidney disease and magnesium-restricted diets 7, but does not list AF as a risk
- Common side effects are gastrointestinal (50% in supplementation studies) 8, not cardiac arrhythmias
Important Caveat
While higher magnesium is generally protective, one exploratory analysis suggested a trend toward slightly higher postoperative ionized magnesium in CABG patients who developed AF 9. However, this was an exploratory finding in a specific surgical subgroup and contradicts the preponderance of evidence showing low magnesium increases AF risk.
Bottom line: Magnesium citrate supplementation does not cause atrial fibrillation and may actually help prevent it, particularly in patients with low baseline magnesium levels.