Signs of low magnesium: symptoms and who is at risk

What are the symptoms of low magnesium?

According to the US National Institutes of Health, early signs of magnesium deficiency include:

• loss of appetite
• nausea and vomiting
• tiredness and weakness

As it becomes more severe:

• numbness and tingling
• muscle cramps, twitching and spasms
• tremor
• personality or mood changes
• abnormal heart rhythms
• in severe cases, seizures

Severe deficiency often comes with low calcium and low potassium too, because magnesium is needed to keep both in balance. That is why doctors often check all three together.

Who is at risk of low magnesium?

• People on long-term proton pump inhibitors such as omeprazole, lansoprazole or esomeprazole (see medicines and magnesium). The MHRA warned in 2012 that taking them for more than a year can cause low magnesium, sometimes severe, and that doctors should consider checking levels before and during long-term treatment.
• People taking loop or thiazide diuretics, such as furosemide or bendroflumethiazide, which increase losses in urine.
• People with type 2 diabetes, particularly if blood sugar is high.
• Heavy drinkers. Alcohol increases losses and is often linked to a poor diet.
• People with gut conditions such as Crohn’s disease, coeliac disease, long-lasting diarrhoea, or after weight-loss or bowel surgery.
• Older adults, who absorb less magnesium and lose more through the kidneys.

When should you see a GP?

See your GP if you have persistent cramps, twitching, tingling or weakness, especially if you are in one of the groups above. Get urgent help if you have palpitations with dizziness or fainting, chest pain or a seizure.

A GP can arrange a blood test and look for the underlying cause. Treating a confirmed deficiency usually means oral magnesium, or a drip in hospital if it is severe, along with dealing with the cause, for example reviewing a medicine.

Can low magnesium cause anxiety, poor sleep or tiredness?

It can, when the deficiency is real: tiredness, weakness and mood changes are on the list above. But these symptoms are so common, and have so many other causes, that they are a poor guide on their own. Trials of magnesium for sleep and anxiety found small or uncertain effects in people with normal levels, and the best trials for night-time leg cramps found it no better than placebo. If you have one of the risk factors above as well as symptoms, a test is the way to find out.

Can a supplement prevent it?

For people with a clear risk, such as long-term PPI users, a doctor may recommend a supplement after testing. For everyone else, a diet with plenty of magnesium-rich foods is the best protection. How much magnesium you need gives the UK daily amounts. Taking a supplement on the strength of vague symptoms rarely helps and can hide the real cause.