Does Magnesium Lower Heart Rate? Here’s What the Science Says

Magnesium helps regulate heart rate and maintain stable heart rhythm. Malorny / Getty Images

• Magnesium supports normal heart rhythm by regulating electrical signals in the heart, but supplementation usually won’t lower heart rate unless someone has a deficiency or an arrhythmia.
• IV magnesium may modestly help lower heart rate in people with atrial fibrillation, while oral magnesium may have effects on other aspects of heart health.
• Chronic low magnesium intake is linked to higher risks of heart problems, but taking too much magnesium—especially from supplements—can cause side effects.

Magnesium helps to maintain a steady heart rate by controlling the electrical signals that trigger each beat.¹ Supplements are unlikely to lower heart rate in most healthy people, although they may be helpful for those with certain heart rhythm problems or a magnesium deficiency.

Can Magnesium Help With a Rapid Heartbeat?

Magnesium supplementation usually won't lower your heart rate unless you have a specific heart rhythm problem or a magnesium deficiency (low magnesium levels in the blood).¹

Some studies have suggested that intravenous (IV, into the vein) magnesium given in a hospital setting can help lower heart rate in people with atrial fibrillation (AFib) which is characterized by a rapid and irregular heartbeat.² These treatments are different than taking a magnesium supplement at home, as they are given under medical supervision in much higher doses than daily needs.

In hospital settings, IV magnesium may be combined with other standard-of-care medications (like beta-blockers, calcium channel blockers, or digoxin) to help bring down a rapid heart rate.²

In one study, IV magnesium led to a modestly lower mean heart rate in people with acute AFib.² Studies commonly used doses ranging from 2-5 grams.³²

How Magnesium Helps Control Heart Rate and Rhythm

Magnesium is a key electrolyte that helps to control the electrical impulses that regulate the heart's contractions. It acts as a natural calcium blocker.

Calcium is essential for muscle contraction, including the contraction of the heart muscle. Magnesium regulates the amount of calcium that enters heart cells.¹

By limiting the amount of calcium in heart cells, magnesium helps your heart muscle relax between beats and keeps your heartbeat steady. This process helps regulate heart rate and maintain rhythm (the pattern of heartbeats).⁴

Low magnesium levels can disturb the electrical balance in the heart, increasing the risk of an increased heart rate and destabilized heart rhythm.⁴

Other Ways Magnesium Supports Your Heart

Magnesium can also affect the way your heart works in other ways:

• Exercise tolerance and heart rate recovery: Oral magnesium supplementation has also been shown to improve exercise performance and the heart rate response to exercise in people with coronary artery disease.⁵ However, these effects have not been shown consistently in healthy adults.
• Heart palpitations: Low magnesium levels can affect the electrical signals in the heart, potentially leading heart palpitations.⁶ Palpitations feel like a racing, pounding, or skipping heartbeat. They can range from a minor discomfort to a sign of a more serious arrhythmia.⁷ Routine magnesium supplementation is not a proven treatment for palpitations in otherwise healthy adults without deficiency.
• Blood pressure control: Magnesium supports blood vessel contraction and heart muscle function.⁸ Some studies suggest that oral magnesium may help modestly lower blood pressure in people with a magnesium deficiency, hypertension (high blood pressure), diabetes, prediabetes, or insulin resistance. However, study results have been mixed.⁹¹⁰⁸

Potential Risks of a Magnesium Deficiency

Having a magnesium deficiency doesn't mean you will develop heart disease, but it can increase your likelihood. Chronic low intake or deficiency of magnesium is associated with a higher risk of several heart problems, including:¹¹

• Cardiomyopathy (diseases of the heart muscle causing the walls of the heart chambers to become stretched, thickened, or stiff)
• Congestive heart failure
• Myocardial infarction (heart attack)
• Atherosclerosis (thickening or hardening of the arteries) 
• Coronary vasospasm (narrowing of arteries)

How Much Magnesium Should I Take?

Studies have shown magnesium supplementation may lower blood pressure and improve overall heart health. However, supplementation may only be needed if you do not get enough magnesium through diet.

According to research, a daily intake of 300-600 milligrams (mg) of magnesium may modestly help reduce blood pressure, mainly in people with hypertension and low magnesium intake.¹ However, these doses exceeded the Recommended Daily Amount (RDA) for magnesium from any source (e.g., food, dietary supplements, medications).

If taking magnesium supplements, the following guidance is recommended:

• Follow the RDA, which is 310-420 mg daily for most adults.¹²
• Do not take over 350 mg of magnesium from non-food sources (e.g., dietary supplements) in one day.¹²
• Consult your healthcare provider beforehand, especially if you have kidney disease or pre-existing heart conditions.¹

Higher doses can be used short-term for specific needs under the supervision of a healthcare provider.¹²

Too much magnesium can cause side effects or health problems. High doses can cause diarrhea and stomach cramping, and very high doses can cause low blood pressure.¹²

Always consult your healthcare provider before starting magnesium and for a personalized dosage.

Sources:

1. Fatima G, Dzupina A, Alhmadi HB, et al. Magnesium matters: a comprehensive review of its vital role in health and diseases. Cureus. 2024;16(10):e71392. doi:10.7759/cureus.71392
2. Bhatti H, Mohmand B, Ojha N, Carvounis CP, Carhart RL. The role of magnesium in the management of atrial fibrillation with rapid ventricular rate. Journal of Atrial Fibrillation. 2020;13(4):2389. doi:10.4022/jafib.2389
3. Ramesh T, Lee PYK, Mitta M, Allencherril J. Intravenous magnesium in the management of rapid atrial fibrillation: A systematic review and meta-analysis. J Cardiol. 2021;78(5):375-381. doi:10.1016/j.jjcc.2021.06.001
4. Negru AG, Pastorcici A, Crisan S, Cismaru G, Popescu FG, Luca CT. The role of hypomagnesemia in cardiac arrhythmias: a clinical perspective. Biomedicines. 2022;10(10):2356. doi:10.3390/biomedicines10102356
5. Pokan R, Hofmann P, Duvillard SP von, et al. Oral magnesium therapy, exercise heart rate, exercise tolerance, and myocardial function in coronary artery disease patients. British Journal of Sports Medicine. 2006;40(9):773. doi:10.1136/bjsm.2006.027250
6. Salaminia S, Sayehmiri F, Angha P, Sayehmiri K, Motedayen M. Evaluating the effect of magnesium supplementation and cardiac arrhythmias after acute coronary syndrome: a systematic review and meta-analysis. BMC Cardiovascular Disorders. 2018;18:129. doi:10.1186/s12872-018-0857-6
7. John Hopkins University. Palpitations.
8. Dibaba DT, Xun P, Song Y, Rosanoff A, Shechter M, He K. The effect of magnesium supplementation on blood pressure in individuals with insulin resistance, prediabetes, or noncommunicable chronic diseases: a meta-analysis of randomized controlled trials. The American Journal of Clinical Nutrition. 2017;106(3):921. doi:10.3945/ajcn.117.155291
9. Rosanoff A, Costello RB, Johnson GH. Effectively prescribing oral magnesium therapy for hypertension: a categorized systematic review of 49 clinical trials. Nutrients. 2021;13(1):195. doi:10.3390/nu13010195
10. Zhang X, Li Y, Del Gobbo LC, et al. Effects of magnesium supplementation on blood pressure: a meta-analysis of randomized double-blind placebo-controlled trials. Hypertension. 2016;68(2):324-233. doi:10.1161/HYPERTENSIONAHA.116.07664
11. DiNicolantonio JJ, Liu J, O’Keefe JH. Magnesium for the prevention and treatment of cardiovascular disease. Open Heart. 2018;5(2).
12. National Institutes of Health. Magnesium.

Important Notice: This article was originally published at www.verywellhealth.com by Ayesha Gulzar, PharmD, where all credits are due. Medically reviewed by Paria Sanaty Zadeh, PharmD.

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