Magnesium deficiency can be difficult to spot because its symptoms often overlap with everyday issues such as tiredness, stress, poor sleep and muscle aches.

While severe deficiency is uncommon among healthy people in the UK, low magnesium levels can affect important functions throughout the body, including muscle movement, nerve signalling, energy production and heart health.

Understanding the warning signs, who is most at risk and when supplements may actually help can prevent people from overlooking a potential nutritional issue.

Why Is Magnesium Important for Your Body?

'Magnesium is an essential mineral involved in more than 300 biochemical reactions throughout the body, making it vital for overall health,' says Abbas Kanani, MRPharmS, superintendent pharmacist at Chemist Click.

'It plays an important role in muscle contraction and relaxation, nerve signalling, energy production, maintaining healthy bones and supporting a normal heart rhythm.'

Magnesium also contributes to regulating blood sugar levels, blood pressure and bone health. Because the mineral is involved in so many different functions, low levels may affect several areas of health at once.

What Are the Symptoms of Magnesium Deficiency?

Early signs of magnesium deficiency can be subtle and may be mistaken for other conditions. Common symptoms include:

  • Muscle cramps or twitches
  • Fatigue and weakness
  • Reduced exercise tolerance
  • Headaches
  • Poor sleep
  • Irritability or low mood

However, these symptoms are not specific to magnesium deficiency and can have many other causes.

'In more severe cases, people may experience numbness, tingling, abnormal heart rhythms or muscle spasms, which require medical assessment,' Kanani says.

Because symptoms often develop gradually, magnesium deficiency may go unnoticed until levels become significantly low or another health issue draws attention to it.

How Common Is Magnesium Deficiency?

True magnesium deficiency is not considered extremely common among otherwise healthy people. However, it can still be overlooked because symptoms such as tiredness, muscle discomfort and sleep problems are relatively common.

Kanani explains that these symptoms are often attributed to stress, ageing or other lifestyle factors, meaning magnesium deficiency may not initially be considered.

A diagnosis usually requires looking at the wider picture, including diet, symptoms, medical history and any conditions that could affect magnesium absorption or loss.

Who Is at Risk of Low Magnesium Levels?

Certain groups are more likely to develop low magnesium levels, including people with conditions that affect nutrient absorption or increase magnesium loss.

Those at higher risk may include people with:

  • Crohn's disease, coeliac disease or chronic diarrhoea
  • Poorly controlled type 2 diabetes
  • Alcohol dependence
  • Kidney disorders
  • Reduced dietary intake, particularly among some older adults

Some medicines can also affect magnesium levels. Long-term use of proton pump inhibitors (PPIs) for acid reflux, certain diuretics and some cancer treatments may increase the risk of deficiency.

Anyone taking these medicines for a prolonged period should speak with a healthcare professional if they are concerned about their magnesium levels.

How Is Magnesium Deficiency Tested?

Magnesium levels are usually assessed through a blood test. However, testing has limitations because only a small proportion of the body's magnesium is found in the bloodstream.

'Only around 1% of the body's magnesium is found in the bloodstream, with most stored in bones and inside cells,' Kanani explains.

This means a normal blood magnesium result does not always completely rule out low magnesium stores. Healthcare professionals will typically consider test results alongside symptoms, dietary intake, medications and underlying health conditions.

Which Foods Are High in Magnesium?

Most healthy adults can get enough magnesium through a balanced diet. Good food sources include:

  • Almonds and cashews
  • Pumpkin and sunflower seeds
  • Peanuts
  • Oats
  • Brown rice
  • Quinoa
  • Wholegrain bread
  • Beans such as kidney beans and chickpeas
  • Spinach and kale
  • Tofu
  • Dark chocolate with high cocoa content
  • Oily fish such as mackerel

Including a variety of these foods regularly can help maintain adequate magnesium intake without relying on supplements.

Do Magnesium Supplements Actually Work?

Magnesium supplements can be useful for people with a confirmed deficiency or those who struggle to get enough magnesium through their diet because of certain medical conditions or restrictions.

'There is good evidence that supplementation effectively corrects magnesium deficiency,' Kanani says.

Some research also suggests magnesium supplements may help in specific situations, including reducing migraine frequency for some people and supporting certain pregnancy-related complications under medical supervision.

However, many popular claims about magnesium improving sleep, eliminating anxiety, boosting energy or stopping muscle cramps in everyone are not strongly supported by evidence.

'Magnesium isn't a miracle supplement, and many of these benefits are strongest in people who are genuinely deficient,' Kanani says.

How Much Magnesium Do You Need?

The NHS and Public Health England recommend a daily intake of 300mg for adult men and 270mg for adult women. Most people can achieve this through a healthy, varied diet.

Magnesium from food is considered very safe because the kidneys remove excess amounts. However, high-dose supplements can cause side effects, including:

  • Diarrhoea
  • Stomach cramps
  • Nausea

People with kidney disease may be at greater risk of magnesium levels becoming too high and should seek medical advice before taking supplements.

As a general guide, supplements containing more than around 400mg of elemental magnesium daily are more likely to cause digestive side effects unless recommended by a healthcare professional.

When Should You Speak to a Doctor?

If you experience persistent fatigue, muscle weakness, recurring cramps, numbness, tingling or changes in your heart rhythm, it is important not to assume magnesium deficiency is the cause.

These symptoms can have many explanations, and a healthcare professional can help identify the underlying issue and determine whether testing or supplementation is appropriate.

Magnesium plays an important role in maintaining health, but supplements are not a replacement for a balanced diet or medical assessment when symptoms persist. The best approach is to understand your individual needs rather than relying on broad health claims online.