Can a 120 mg dose of magnesium glycinate cause cardiac arrhythmia in a person with normal renal function and no significant cardiac disease?

Magnesium Glycinate 120mg Does Not Cause Cardiac Arrhythmias

A 120 mg dose of magnesium glycinate will not cause cardiac arrhythmias in a person with normal renal function and no significant cardiac disease; in fact, magnesium supplementation at this dose is protective against arrhythmias and is used therapeutically to treat and prevent them. 1, 2

Why Magnesium Prevents Rather Than Causes Arrhythmias

Magnesium is fundamentally anti-arrhythmic, not pro-arrhythmic. The evidence consistently demonstrates that magnesium:

• Stabilizes cardiac myocyte membranes by regulating calcium and potassium channel function, which prevents rather than triggers arrhythmias 3, 4
• Increases the ventricular threshold for fibrillation, making dangerous arrhythmias less likely to occur 5
• Prolongs sinus node refractoriness and AV node conduction in a protective manner 5
• Is used as first-line treatment for life-threatening arrhythmias like torsades de pointes, with 1-2 g IV doses (far exceeding your 120 mg oral dose) administered safely 1, 3

The Dose Context: 120mg is Modest and Safe

Your 120 mg dose of magnesium glycinate is:

• Well below therapeutic IV doses used to treat arrhythmias (1,000-2,000 mg IV) 1, 3
• Within the range of standard oral supplementation (12-24 mmol daily = approximately 290-580 mg elemental magnesium) recommended for mild deficiency 6
• Unlikely to cause toxicity in someone with normal renal function, as magnesium toxicity typically requires serum levels of 6-10 mmol/L, which occurs almost exclusively with massive IV dosing or severe renal impairment 6

When Magnesium Actually Becomes Problematic

The only scenario where magnesium causes cardiac complications is hypermagnesemia (excess magnesium), which:

• Requires serum levels >2.5 mmol/L to begin causing symptoms, with life-threatening toxicity at 6-10 mmol/L 6
• Causes bradycardia and hypotension at toxic levels, not the tachyarrhythmias most people fear 6
• Occurs almost exclusively in patients with severe renal dysfunction (GFR <30 mL/min) receiving large amounts of magnesium-containing medications, not from standard oral supplementation 6
• Presents with progressive weakness, areflexia, respiratory depression, and cardiovascular collapse—not isolated arrhythmias 6

The Real Clinical Picture: Deficiency Causes Arrhythmias

The evidence overwhelmingly shows that low magnesium, not supplementation, is the arrhythmia risk:

• Hypomagnesemia is classically associated with ventricular arrhythmias including PVCs, polymorphic VT, and torsades de pointes 2, 3
• The American College of Cardiology recommends maintaining serum magnesium ≥2 mEq/L in patients with ventricular arrhythmias 2
• Magnesium deficiency makes concurrent hypokalemia resistant to correction, creating a dangerous electrolyte environment that predisposes to arrhythmias 2, 6, 7
• Low plasma magnesium is associated with poor prognosis in cardiac arrest patients 2, 3

Common Medications That Deplete Magnesium

If you're concerned about arrhythmias, focus on whether you're taking medications that cause magnesium deficiency:

• Loop and thiazide diuretics are the most common causes of renal magnesium wasting 6
• Proton pump inhibitors promote renal magnesium loss 6
• Digoxin toxicity risk increases markedly with magnesium deficiency 1, 6

Bottom Line for Your Specific Situation

With normal renal function and no significant cardiac disease:

• Your 120 mg magnesium glycinate dose is safe and will not cause arrhythmias 6, 4
• If anything, it may be protective against arrhythmias, particularly if you have subclinical deficiency 2, 3, 8
• Magnesium toxicity from oral supplementation is extraordinarily rare in people with normal kidney function 1
• The only monitoring needed is if you develop symptoms of hypermagnesemia (profound weakness, confusion, severe hypotension), which is exceedingly unlikely at this dose 6