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PortugalMagnesium deficiency: symptoms, causes and who is at risk
What are the symptoms of low magnesium, who is most at risk of a deficiency and how is it tested in the UK? And why true deficiency is less common than you’d think.
True magnesium deficiency is uncommon in healthy people who eat a varied diet. The symptoms are vague – tiredness, weakness, nausea, loss of appetite, muscle cramps, twitching or trembling – and usually have other causes. The risk is higher with heavy drinking, some gut conditions, type 2 diabetes and long-term use of certain medicines. If you think you might be low, see your GP.
How common is magnesium deficiency?
A true deficiency – low magnesium in the blood, which doctors call hypomagnesaemia – is uncommon in healthy people. Magnesium is in lots of everyday foods, and when your intake drops, your kidneys hold on to more of it.
A low intake is more common than a deficiency, though. The UK’s National Diet and Nutrition Survey (2016 to 2019) found around 1 in 9 adults have magnesium intakes below the lower reference nutrient intake, and among teenagers it’s about a third of boys and nearly half of girls. Eating less than you need for a while isn’t the same as being deficient – your body keeps a store, mostly in your bones and muscles.
What are the symptoms of low magnesium?
Early symptoms are non-specific and easy to put down to something else:
- tiredness and weakness
- loss of appetite, nausea or being sick
- muscle cramps, twitching or trembling
A more severe deficiency can cause pins and needles, muscle spasms, an irregular heartbeat and, rarely, seizures. That needs medical treatment – it isn’t something to manage with supplements on your own.
Can low magnesium cause anxiety or poor sleep?
You’ll often read online that low magnesium causes anxiety, low mood or insomnia. These aren’t established symptoms of magnesium deficiency, and all of them have many possible causes – stress, hormonal changes, other health conditions. If they’re affecting your life, talk to your GP rather than treating yourself.
Who is at risk of magnesium deficiency?
The risk is higher if something affects how much magnesium you absorb or lose:
- Drinking a lot of alcohol, which increases the magnesium lost in urine and often goes with a poorer diet.
- Gut conditions such as Crohn’s disease and coeliac disease, or long-lasting diarrhoea.
- Type 2 diabetes, where more magnesium can be lost through the kidneys.
- Certain medicines, such as some diuretics (water tablets) and proton pump inhibitors for acid reflux (for example omeprazole and lansoprazole) – with proton pump inhibitors, usually after a year or more of use.
- Older age, as people often eat less.
- A very restricted or limited diet.
How do you test for magnesium deficiency?
Your GP can arrange a blood test. The NHS says a magnesium test may be recommended as part of a series of tests if you have symptoms such as nausea, weakness, twitching, cramping or an irregular heartbeat, because levels of magnesium, calcium or potassium may be low.
A blood test doesn’t tell the whole story: most of your body’s magnesium is stored in your bones and other tissues, and only a small fraction is in your blood. A normal result doesn’t completely rule out low stores, so your GP will also consider your symptoms, other conditions and any medicines you take.
How do you raise your magnesium levels?
It depends on the cause and how low you are. If your intake is just on the low side, eating more magnesium-rich foods is usually enough – see Magnesium-rich foods. Your GP may recommend a supplement, and a more serious deficiency is treated by doctors, sometimes in hospital.
If you take a supplement on your own, stay at or below 250 mg of magnesium a day and read more in How much magnesium do you need per day?
Frequently asked questions
What are the 7 signs your body needs magnesium?
Lists like this circulate widely online, but there’s no official “seven signs”. The recognised symptoms of low magnesium are tiredness, weakness, nausea, loss of appetite, and muscle cramps, twitching or trembling – all of which have many other causes. Only a blood test, alongside a GP’s assessment, can tell you.
Can low magnesium cause leg cramps?
Muscle cramps can be a symptom of low magnesium, but leg cramps are common and usually have other causes, such as ageing, overdoing exercise, pregnancy, some medicines or dehydration. If you get them often, see your GP.
What do you crave if your magnesium is low?
You’ll often read that chocolate cravings are a sign of low magnesium. There’s no good evidence for that. Cravings are much more likely to be about habit, mood or hunger.
Can I check my magnesium level at home?
There’s no reliable home test. A standard blood test through your GP is the usual way to check, and the result needs interpreting alongside your symptoms and medical history.
How quickly can you raise your magnesium level?
It depends on the cause and how low your levels are. With a serious deficiency, doctors monitor you with repeat blood tests. If your intake is just a bit low, the most important thing is eating a varied diet consistently.
Can exercise cause magnesium deficiency?
You lose a little magnesium in sweat, but healthy people who exercise and eat a varied diet normally get enough. Magnesium contributes to normal muscle function and electrolyte balance.
Sources
- NHS – Magnesium test
- NHS – Vitamins and minerals: Others (magnesium)
- British Nutrition Foundation – Vitamins and minerals
- NHS – Leg cramps
- MHRA Drug Safety Update – Proton pump inhibitors in long-term use: reports of hypomagnesaemia
- EFSA – Tolerable Upper Intake Levels for vitamins and minerals (2006)
- GOV.UK – National Diet and Nutrition Survey
