Magnesium Deficiency: Signs, Causes & Best Sources

What Is Magnesium?

Magnesium is an essential mineral involved in over 300 enzymatic reactions in the body — more than almost any other nutrient. It’s stored mainly in bone and muscle tissue, and only about 1% circulates in the blood, which is part of why a standard blood test doesn’t always catch a mild, long-standing shortfall.

Why Your Body Needs It

Under EU Regulation (EC) 1924/2006, magnesium carries a wide range of authorised health claims — more than most single nutrients, reflecting how many systems it supports:

  • Contributes to normal muscle function and normal functioning of the nervous system
  • Contributes to normal psychological function
  • Contributes to the reduction of tiredness and fatigue
  • Contributes to electrolyte balance
  • Contributes to normal energy-yielding metabolism
  • Contributes to normal protein synthesis
  • Contributes to the maintenance of normal bones and normal teeth
  • Has a role in the process of cell division

Signs of Magnesium Deficiency

True, clinically diagnosed magnesium deficiency is relatively uncommon in healthy people, but sub-optimal intake is thought to be widespread — surveys suggest a large share of UK/EU adults don’t reach recommended intakes through diet alone. When levels run low, the most commonly reported signs include:

  • Muscle cramps or twitches, particularly in the calves
  • Fatigue and general weakness
  • Loss of appetite, nausea
  • Difficulty relaxing, sleep disturbances
  • Tension headaches
  • In more pronounced cases: numbness, tingling, or heart palpitations — these warrant a GP visit, not self-treatment

Who’s Most at Risk

  • People with high stress levels or heavy training loads, both of which increase magnesium turnover
  • People who drink alcohol regularly, which increases urinary magnesium loss
  • Anyone on long-term proton pump inhibitors (PPIs) or certain diuretics
  • People with gastrointestinal conditions affecting absorption (Crohn’s, coeliac disease, chronic diarrhoea)
  • People with type 2 diabetes
  • Older adults, whose absorption efficiency and dietary intake often decline with age

How Much Do You Need?

UK and EU reference intakes sit in a similar range: broadly around 300–420mg/day for adult men and 270–320mg/day for adult women, varying slightly by country and body weight. Most multivitamins provide only a fraction of this, which is why magnesium is often taken as a standalone supplement when intake is a concern.

Food Sources

  • Pumpkin seeds, chia seeds, and almonds
  • Leafy green vegetables (spinach, Swiss chard)
  • Legumes (black beans, chickpeas)
  • Wholegrains
  • Dark chocolate (70%+ cocoa)

Modern soil depletion and food processing mean many diets fall short of these amounts even when eating reasonably well — one reason magnesium ranks among the more commonly supplemented minerals in the UK/EU.

Choosing a Magnesium Supplement

Form matters more with magnesium than with most minerals:

  • Bisglycinate (glycinate) — bound to the amino acid glycine, well absorbed and generally gentle on the stomach; a common choice for sleep and relaxation
  • Citrate — well absorbed, but can have a mild laxative effect at higher doses
  • Oxide — cheap and common in budget multivitamins, but poorly absorbed relative to other forms
  • Check the elemental magnesium content on the label, not just the total compound weight — this is what actually counts toward your daily intake

Our pick: Magnesium Bisglycinate 500mg — a well-absorbed, stomach-friendly form suited to daily use.


Wondering if magnesium is your missing piece?

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This page is for general educational purposes only and is not medical advice. Persistent cramping, palpitations, or numbness should be discussed with a GP.


Sources & Further Reading

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