This article is for general information only and is not medical advice. If you have a heart condition, high or low blood pressure, kidney disease, or take prescribed medicine, speak to your doctor or pharmacist before taking magnesium. Never use a supplement in place of prescribed treatment.
The short answer
Magnesium is essential for a normal heartbeat and healthy blood vessels, and getting enough from your diet is part of looking after your heart. Supplements can lower blood pressure a little. Beyond that, there is no good evidence that magnesium supplements prevent or treat heart disease, and no form has been shown to be better for the heart than another. If you have a heart condition or palpitations, the first step is your GP, not a supplement.
Call 999 if you have chest pain that doesn’t go away, or palpitations with chest pain, breathlessness, or feeling faint.
What magnesium does for the heart
Magnesium helps control the movement of potassium and calcium in and out of heart muscle cells, which is what keeps the heartbeat regular. It also helps blood vessels relax. A marked magnesium deficiency can cause abnormal heart rhythms, according to the NIH.
What the research shows
Blood pressure
This is where the evidence is strongest. A 2016 analysis of 34 trials involving about 2,000 people found that magnesium supplements, at a typical dose of around 370 mg a day for three months, lowered blood pressure by about 2 mmHg on average. That is a real but small effect, far less than blood pressure medicine achieves, and not a reason to change any treatment you have been prescribed.
Heart disease and stroke
Studies that follow large groups of people over time tend to find that those who eat more magnesium-rich foods have slightly lower rates of heart disease and stroke. These studies can’t show that magnesium is the reason, because the same people usually eat more vegetables, nuts and whole grains overall. Trials have not shown that taking magnesium supplements prevents heart attacks or strokes.
Palpitations and heart rhythm
Doctors sometimes give magnesium through a drip in hospital to treat certain rhythm problems. That is a different situation from taking tablets at home. There is little reliable evidence that magnesium supplements stop palpitations in people whose magnesium levels are normal. An earlier version of this article relied on a 1990 observational study with no comparison group to suggest they do. We have removed that claim.
Most palpitations are harmless and are linked to stress, caffeine, alcohol or lack of sleep. The NHS advises seeing a GP if they keep coming back, last longer than a few minutes, or if you have a heart condition or a family history of heart problems.
Which form of magnesium?
No trial has shown that one form is better for the heart than another. The practical differences are in how well each is absorbed and how it affects your digestion.
| Form | What to know |
|---|---|
| Citrate | Well absorbed. Loosens stools at higher doses. |
| Glycinate (bisglycinate) | Well tolerated and gentle on the stomach. Can feel sedating. |
| Taurate | Often marketed for heart health. Very little research in people. |
| Oxide | Cheap and widely used in trials. Less well absorbed and more likely to cause diarrhoea. |
Choose the one you tolerate best. If you want to compare products, see our magnesium glycinate reviews.
How much
The NHS says adults need about 300 mg (men) or 270 mg (women) of magnesium a day, and that 400 mg or less a day from supplements is unlikely to cause harm. Higher doses can cause diarrhoea.
Food is the best place to start. Nuts, seeds, leafy green vegetables, beans and whole grains are all good sources, and they bring fibre and potassium with them.
Magnesium and heart medicines
Check with your pharmacist or doctor before taking magnesium if you take:
- Blood pressure medicines, as magnesium may add slightly to their effect.
- Water tablets (diuretics). Some lower magnesium levels and others raise them.
- Digoxin or other heart rhythm medicines. Your doctor may want to check your magnesium and potassium levels.
- Some antibiotics, osteoporosis medicines and thyroid tablets. Magnesium can stop these being absorbed, so they need to be taken at different times.
If you have kidney disease, don’t take magnesium unless your doctor has advised it. The kidneys clear excess magnesium, and it can build up to harmful levels.
See how magnesium interacts with other nutrients
Magnesium works closely with potassium and calcium in the heart. Tap magnesium on our free Mineral Interaction Wheel to see which nutrients it works with and which it may compete with. If magnesium makes you feel worse, our magnesium side effects guide explains what to try.
Sources
- NIH Office of Dietary Supplements. Magnesium: Fact Sheet for Health Professionals.
- Zhang X, et al. Effects of magnesium supplementation on blood pressure: a meta-analysis of randomized double-blind placebo-controlled trials. Hypertension, 2016.
- NHS. Vitamins and minerals: Others (magnesium).
- NHS. Heart palpitations.