Magnesium Glycinate and Heart Palpitations
Magnesium glycinate does not cause heart palpitations in therapeutic doses; rather, magnesium deficiency is the primary cause of cardiac arrhythmias and palpitations, while excessive magnesium intake leading to hypermagnesemia can cause bradycardia and conduction abnormalities—not palpitations.
Magnesium's Protective Role Against Arrhythmias
Magnesium deficiency, not supplementation, is associated with ventricular arrhythmias including premature ventricular contractions (PVCs), ventricular tachycardia, and torsades de pointes 1, 2.
Low serum magnesium concentrations are linked to increased risk of cardiac arrhythmias and poor prognosis in cardiac arrest patients 1, 2.
In heart failure patients with hypomagnesemia, intravenous magnesium administration significantly decreased premature ventricular depolarizations from 794 ± 309 to 369 ± 223 per hour in those with frequent arrhythmias 3.
Magnesium supplementation in heart failure patients demonstrated significantly fewer PVCs after treatment 1.
Cardiovascular Effects of Therapeutic Magnesium
Magnesium increases ventricular threshold for fibrillation and prolongs sinus node refractoriness and AV node conduction—effects that suppress rather than cause arrhythmias 4.
Intravenous magnesium is effective for treating supraventricular arrhythmias, with 58% conversion to sinus rhythm within 4 hours compared to 19% with verapamil, without causing palpitations 5.
The American College of Cardiology recommends maintaining magnesium >2 mg/dL to prevent torsades de pointes and drug-induced arrhythmias in patients with cardiac arrhythmias or QT prolongation 1.
Hypermagnesemia: The Actual Cardiac Risk
When excessive magnesium causes toxicity, the cardiovascular manifestations are bradycardia and conduction blocks—not palpitations or tachycardia:
At moderate hypermagnesemia (2.5-5 mmol/L or 6-12 mg/dL), ECG changes include prolonged PR, QRS, and QT intervals, along with vasodilation and hypotension 6, 7.
Severe hypermagnesemia (6-10 mmol/L or >12 mg/dL) causes atrioventricular nodal conduction block, bradycardia, and cardiac arrest 6, 7.
The American Heart Association notes that hypermagnesemia results from excessive intake combined with impaired renal excretion, particularly with creatinine clearance <20 mL/min 6.
Special Considerations for High-Risk Populations
Patients with pre-existing heart conditions or on cardiac medications should be aware of these specific interactions:
Concurrent administration of high-dose magnesium with ibutilide (a Class III antiarrhythmic) has been associated with enhanced efficacy and safety in treating arrhythmias 8.
Magnesium is used therapeutically for drug-induced torsades de pointes, with intravenous magnesium sulfate recommended even when serum magnesium is normal 8.
Heart failure patients on diuretics are at high risk of magnesium deficiency and should have levels monitored closely, as hypomagnesemia is associated with more frequent ventricular arrhythmias 1.
Renal dysfunction is the primary risk factor for hypermagnesemia, with creatinine clearance <20 mL/min representing an absolute contraindication to magnesium supplementation 6.
Clinical Bottom Line
For patients experiencing palpitations while taking magnesium glycinate:
Check serum magnesium levels to rule out hypermagnesemia (though this is rare with oral supplementation in patients with normal renal function) 6.
Assess renal function, as impaired kidney function is the most important predisposing factor for magnesium accumulation 6.
Consider that palpitations may be coincidental or related to underlying magnesium deficiency that is being corrected, rather than caused by the supplement 1, 2.
If magnesium levels are elevated (>2.5 mmol/L), expect bradycardia and conduction delays rather than palpitations 7.
Magnesium glycinate is generally well-tolerated with minimal gastrointestinal side effects compared to other magnesium formulations, and cardiovascular side effects from therapeutic doses are exceptionally rare in patients with normal renal function 6.