Complications and Risks of Magnesium Deficiency

Untreated low magnesium can cause serious problems, particularly when it is severe or comes with low potassium and calcium.

Heart problems

• Abnormal heart rhythms, including a serious rhythm called torsades de pointes
• Palpitations, fainting and, rarely, cardiac arrest
• Higher risk if you have heart disease or take digoxin

Nerve and muscle problems

• Cramps, tremor, spasms and weakness
• Tingling and numbness
• Seizures in severe cases

Other electrolyte problems

• Low potassium that does not correct until magnesium is replaced
• Low calcium and in some cases tetany

Long-term effects of low magnesium

Long-term low intake has been linked in studies with higher risk of type 2 diabetes, high blood pressure, bone loss and migraine. These links do not prove that supplements prevent these conditions.

Mood and mental effects

Irritability, anxiety, low mood and confusion may occur.

Risks from too much magnesium

Over-treatment can cause harm, especially in kidney disease:

• Diarrhoea
• Low blood pressure, drowsiness and slow breathing at high levels

Do not take high doses without a doctor.

Warning signs needing urgent care

Seizures, fainting, severe weakness, chest pain, very fast, slow or irregular heartbeat. Call 112.

Reducing risk

Treat the cause, eat a balanced diet, limit alcohol and have blood tests if you are at risk.

Key point

Heart rhythm problems and seizures are the main dangers, and both are preventable with timely treatment.

Before your appointment

Note your symptoms, when they began, and what makes them better or worse. Mention alcohol use, diarrhoea, vomiting, diabetes, kidney disease, bowel conditions and any recent illness. List all medicines, especially diuretics, acid-reducing medicines, antibiotics, supplements and herbal products. Write down your usual diet and any antacids or laxatives you take. Ask about blood tests for magnesium, potassium and calcium, and whether an ECG is needed. Call 112 for seizures, fainting, severe weakness or a very irregular heartbeat.