Magnesium tablets are everywhere — but are they truly the wonder fix they're made out to be?

From pharmacy shelves to influencer posts, magnesium supplements are being promoted as miracle aids for everything from better sleep to muscle cramps. But health experts warn that while magnesium is essential, popping supplements without medical advice might be unnecessary — or even harmful.

What is magnesium and why is it important?

Magnesium is a vital mineral your body needs to function properly. It plays a role in over 300 enzyme processes — helping muscles contract, nerves function, energy release from food, and even supporting heart and blood vessel health.

Unlike some nutrients, the body can't make magnesium. It has to come from external sources, particularly food. Fortunately, that’s not hard: magnesium is found in everyday items like green leafy vegetables, legumes, whole grains, nuts, seeds, seafood, and even dark chocolate (which offers a surprising 146 mg per 100 g).

According to government guidelines, adults should aim for 310–420 mg of magnesium a day, while children need between 30 and 410 mg depending on their age.

Do you need a supplement? Probably not.

For most people, a balanced diet provides all the magnesium they need. But certain groups may be at risk of deficiency — including those with gastrointestinal disorders (such as Crohn’s or coeliac disease), people with type 2 diabetes, alcohol dependence, or older adults. Restricted diets can also increase risk.

Signs of low magnesium include muscle spasms or twitches, loss of appetite, nausea, vomiting, and irregular heartbeats. If you suspect a deficiency, doctors can order a blood test — and it’s covered by Medicare.

Supplements: hype or help?

Magnesium supplements are heavily marketed to assist with cramps, insomnia, and migraines. But the science is mixed.

While magnesium deficiency can contribute to cramps, "the cause of most muscle cramps remains unknown," and studies show magnesium doesn’t consistently relieve them in older adults.

As for sleep, results are also inconclusive. One study found magnesium could reduce the time it takes to fall asleep by 17.4 minutes, but other trials found little to no effect.

For migraines, there's better news. Research suggests that 122–600 mg of magnesium daily for up to 24 weeks may reduce the frequency and severity of migraine attacks.

Can you take too much magnesium?

In most cases, magnesium supplements are well tolerated. But they can cause side effects — especially in high doses — including nausea, abdominal cramps, and diarrhoea. “Magnesium causes diarrhoea by drawing water into the intestine and stimulating movement in the gut,” experts explain.

More worryingly, very high doses — around 5,000 mg a day — can lead to magnesium toxicity, a potentially serious condition.

What about creams and sprays?

Magnesium is a small ion and can pass through the skin to some extent, which is why bath salts, topical creams, and patches are popular. However, experts say these aren't reliable sources for meeting daily needs. “Due to the amount needed each day, tablets and foods are a better source,” the evidence suggests.

A word of caution on supplement combos

Magnesium supplements can vary widely in formulation, often containing between 150 and 350 mg per tablet. They also may include other nutrients like vitamin C, D, calcium, chromium, manganese, or B6 — the last of which can cause serious health issues if consumed in excess.

“If you're already taking a B6 supplement, a magnesium supplement that also includes it can put you at risk,” experts warn.

Bottom line: Talk to your doctor first

If you’re experiencing cramps, poor sleep, or migraines and are considering magnesium supplements, health professionals recommend speaking to a doctor or pharmacist first. They can help determine whether you truly need supplementation — or if other underlying issues are at play.

Magnesium may be essential, but in most cases, you can get enough from what’s already on your plate.