How magnesium may help with insomnia, heartburn and high blood pressure: why this supplement is so popular and the best way to take it

Magnesium has quickly become one of the most talked-about supplements on the market, with social media packed with claims that it can help with everything from sleep and memory to muscle strength.

Holland and Barrett has named magnesium its most popular supplement of 2025, with 45 million capsules sold. At the same time, the global magnesium market is expected to almost double over the next decade.

So why is it attracting so much attention?

Research shows magnesium is one of the body’s most important minerals, involved in about 300 essential functions.

It supports everything from healthy cells, organs and brain function to the muscles, nervous system and immune system, and it also helps keep mood stable.

One large study by Australian researchers published last year even suggested that magnesium supplements may lower blood pressure.

The challenge is that the body cannot make magnesium itself, so we rely on food sources that are not always common in the British diet, such as nuts, seeds, fish like mackerel and dark leafy greens.

Studies suggest that nearly 60% of Britons do not get enough. So should everyone take a supplement, and if so, which form is best? Experts explain the mineral everyone is suddenly talking about.

Who should take magnesium, and how much is too much?

Official figures indicate that most Britons are not eating as much magnesium as they need.

The NHS recommends that women aged 19 to 64 aim for about 270mg a day, while men in the same age group are advised to get around 300mg.

About 100g of several magnesium-rich foods provides roughly 270mg. These include almonds, cashew nuts and pumpkin seeds.

Dark leafy vegetables such as kale and spinach are also good sources, as are oats and most legumes.

Even better, just two squares of dark chocolate — ideally 85% cocoa or higher — contain about 100mg of magnesium.

You can also increase your intake with supplements, which are widely sold as 375mg tablets for as little as 10p per dose.

But experts say supplements are not necessary for everyone.

“If you’re already eating a high-magnesium diet or are taking a medicine that interacts with the mineral, it may not be recommended,” says Alex Glover, senior nutritionist at Holland and Barrett.

“But it can be quite difficult from a nutritional perspective to get that level of magnesium every day, so supplementation can be helpful.”

The NHS advises keeping magnesium intake to no more than 400mg a day because higher doses can cause diarrhoea and, at very high levels, blood pressure and heart rhythm problems.

Sleep and neurology specialist Dr Hanul Bhandari adds: “Magnesium supplements are highly effective for correcting a deficiency and easing its symptoms, but taking extra magnesium when levels are already normal will not provide additional health benefits.

“Anyone with heart block, the autoimmune condition myasthenia gravis, or kidney disease should speak to a clinician before taking magnesium supplements.

“For most healthy people, however, the body will naturally get rid of excess magnesium absorbed from food.”

Which type should I buy?

Choosing a magnesium supplement can be confusing because there are many forms available, often combined with other compounds such as glycinate, citrate and L-threonate.

Experts say the paired compound can influence how easily it dissolves, how well it is absorbed and how it is typically used.

That means the first step is deciding what you want the supplement to do.

Magnesium glycinate, also known as magnesium bisglycinate, is commonly used by people looking to improve sleep.

Glycinate is involved in normal nerve and muscle function, which may help calm the body and make sleep easier.

In a randomized, double-blind trial in 2025, 155 adults with poor sleep took either 250mg of elemental magnesium from bisglycinate or a placebo each day for four weeks.

The magnesium group reported a small but statistically significant improvement in sleep-related symptoms, with greater benefits among those whose diets were lower in magnesium at the start.

Another meta-analysis found that magnesium reduced the time it took older adults to fall asleep by around 17 minutes.

“Magnesium helps regulate melatonin, the sleep hormone, and supports GABA, a calming neurotransmitter in the brain,” says nutritionist Dr Naomi Newman-Beinart.

“It isn’t a sleeping pill, but it can make it easier to relax and drift off naturally.”

Experts also say magnesium glycinate and magnesium taurate may be especially helpful for blood pressure and heart health.

“Magnesium is really important in regulating blood pressure,” says Mr Glover. “It may be the effect we have the strongest evidence for.”

Research indicates that the mineral can help blood vessels relax and widen, lowering blood pressure.

Clinical studies have shown that magnesium supplements can significantly reduce blood pressure, although the clearest effects were seen in people who already had high blood pressure or low magnesium levels.

Magnesium citrate can also work as a laxative while increasing the body’s magnesium stores.

“When you take magnesium orally, as a pill or powder, it has to pass through your digestive system before your body can use it,” says Dr Newman-Beinart.

“Some forms, such as magnesium citrate, can sometimes cause digestive upset.”

Magnesium L-threonate is often more expensive and is heavily marketed for cognitive support because it was developed with brain health in mind.

Research suggests magnesium is important for neurological health because it helps calm overactive brain signals, protects the blood-brain barrier and reduces inflammation linked to cognitive decline.

Some studies have found that a higher magnesium intake is associated with greater brain volume and a lower risk of cognitive impairment.

Animal research has shown that magnesium L-threonate raises magnesium levels in the brain and affects synaptic plasticity, which is involved in learning and memory.

Human research remains limited, but a trial involving 100 adults aged 18 to 45 who took 2g of magnesium L-threonate daily found improved scores on several cognitive tests, including those measuring working and episodic memory.

Dr Bhandari adds that some magnesium-containing antacids are designed for quick, short-term relief of occasional heartburn.

These products usually combine magnesium with compounds that neutralise stomach acid, such as magnesium hydroxide, magnesium carbonate or magnesium trisilicate.

Once they reach the stomach, he explains, they rapidly reduce acidity, easing heartburn or indigestion and relaxing muscles in the gastrointestinal tract.

Also called milk of magnesia, magnesium hydroxide is used in several well-known laxatives, including Dulcolax.

When should I take it, and what about creams and salts?

Dr Newman-Beinart says magnesium can be taken at any time of day.

“However, because of its calming effect on the nervous system, many people find it especially useful in the evening, when it may support relaxation and help prepare the body for sleep,” she says.

Magnesium can also be used to ease restless legs syndrome, in which the lower legs become intensely twitchy and tingly at night.

For this, many people use magnesium creams, bath salts or sprays, which are thought to be well absorbed and may help with muscle cramps.

Magnesium citrate, meanwhile, is best taken with food, according to Alex Glover.

Taking it with meals, he says, can help reduce stomach upset, nausea and diarrhoea.