Medicines and Products for Magnesium Deficiency

Treatment of low magnesium depends on how low the level is and why. A doctor should guide it.

Oral magnesium supplements

• Used for mild to moderate deficiency
• Forms include magnesium oxide, citrate, glycinate, lactate and chloride
• Common side effects are diarrhoea, nausea and stomach cramps. Taking smaller doses with food or choosing a different form may help.
• Your doctor decides the dose and duration. Doses above the upper limit for supplements, around 350 mg a day of elemental magnesium for adults, should only be taken on medical advice.

Intravenous magnesium

Given in hospital for severe deficiency, seizures, abnormal heart rhythm or when oral treatment is not possible. Levels are monitored.

Treating the cause

• Reducing or stopping alcohol
• Treating diarrhoea or malabsorption
• Reviewing medicines such as diuretics and acid-reducing medicines, never stop them without advice
• Controlling diabetes
• Correcting low potassium and low calcium

Interactions and cautions

• Magnesium can reduce absorption of some antibiotics (tetracyclines, quinolones), thyroid medicine, bisphosphonates and iron. Take them several hours apart as advised.
• People with kidney disease can build up dangerous magnesium levels and should only take it under medical guidance.
• Magnesium-containing antacids and laxatives can cause problems when used regularly.
• Pregnant and breastfeeding women should ask before use.
• Do not give supplements to children without a doctor's advice.

Key point

Use supplements only on advice, treat the cause, and note that kidney disease needs special care.

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.