Magnesium supplements and high blood pressure: what the guidance says

The NHS describes magnesium as a mineral that helps turn the food we eat into energy and helps make sure the parathyroid glands, which produce hormones important for bone health, work normally. It is found in a wide variety of foods, including spinach, nuts and wholemeal bread. The NHS says most people should be able to get all the magnesium they need by eating a varied and balanced diet.

Low magnesium can be a problem for some people with particular medical conditions or medicines, and is covered separately under magnesium deficiency. This page is about whether adding extra magnesium as a supplement is a way to treat high blood pressure.

NICE guideline NG136 on hypertension in adults says clearly: do not offer calcium, magnesium or potassium supplements as a method for reducing blood pressure. The recommendation applies to people being assessed and treated for high blood pressure in the NHS, and it reflects a judgement that supplements are not an effective or reliable way to lower blood pressure.

This does not mean magnesium is unimportant. It means that people with high blood pressure are better served by the measures listed below and, where needed, by prescribed blood pressure medicines, than by a supplement. Marketing claims that magnesium will normalise blood pressure should be treated with caution.

The NHS says high blood pressure does not usually cause symptoms, so the only way to find out is to get it checked, and lists helpful lifestyle changes: a healthy balanced diet, regular exercise aiming for at least 150 minutes a week, losing weight if overweight, eating less salt, not drinking too much alcohol, not drinking too much caffeine, and not smoking.

NICE similarly recommends asking about diet and exercise because a healthy diet and regular exercise can reduce blood pressure, encouraging people to keep dietary sodium intake low, encouraging a reduced alcohol intake in people who drink excessively, and discouraging excessive consumption of coffee and other caffeine-rich products. NICE also notes that salt substitutes containing potassium chloride should not be used by older people, people with diabetes, pregnant women, people with kidney disease and people taking some blood pressure medicines such as ACE inhibitors and angiotensin II receptor blockers.

Blood Pressure UK notes that eating your 5-a-day of fruit and vegetables can lower blood pressure, that too much salt can raise it, and that potassium is a mineral that helps to lower it. A diet rich in vegetables, nuts and wholegrains will also provide magnesium.

• Eat plenty of fruit, vegetables, wholegrains, nuts and pulses.

• Cut back on salt, including hidden salt in processed foods.

• Be active for at least 150 minutes a week.

• Keep alcohol within 14 units a week and limit caffeine.

• Stop smoking and aim for a healthy weight.

The NHS gives the amount needed as 300mg a day for men and 270mg a day for women aged 19 to 64. It says taking high doses of magnesium, more than 400mg, for a short time can cause diarrhoea, that there is not enough evidence to say what the effects might be of taking high doses for a long time, and that taking 400mg or less a day from supplements is unlikely to cause harm.

If you take regular medicines or have a long-term condition, ask a pharmacist whether a supplement is suitable for you. The NHS also says that if you take magnesium supplements you should not take too much, as this could be harmful.

The NHS says to get your blood pressure checked at a pharmacy or GP surgery if you think you might have high blood pressure, or if you are 40 or over and have not had it checked for more than 5 years. It advises getting help from NHS 111 if you often have headaches or blurred vision, have chest pain that comes and goes, or have other symptoms you are worried could be caused by high blood pressure, and calling 999 for sudden chest pain or discomfort that does not go away, particularly if it spreads to the arm, neck, jaw or back, as it could be a heart attack.

The NHS says that a person is usually considered to have high blood pressure if the reading is 140/90 or higher when checked by a healthcare professional, or 135/85 or higher when checked at home, confirmed with home monitoring or a 24-hour monitor. A GP will usually prescribe medicine if blood pressure is very high, if you are at higher risk of problems such as a heart attack or stroke, or if it is still high after healthy lifestyle changes. Most blood pressure medicines are taken as tablets once a day, and you may need more than one.

Treatment is worth it: the NHS says lowering blood pressure even a small amount can help reduce the risk of heart disease, heart attacks, strokes, heart failure, kidney disease and vascular dementia.

Blood pressure checks are available through GP surgeries and many pharmacies. Private clinics may sell supplement-based programmes, but the national guidance does not support supplements as a treatment for high blood pressure. Tell your GP or pharmacist about any supplement you take.