Description Magnesium is an essential mineral. It is the second most abundant nutrient stored in body tissue after calcium.
Function/ Used for Magnesium is needed for the formation of many enzymes in the body which release energy from food. It is also vital for the nervous system, muscle movement and for the formation of healthy bones and teeth.

Magnesium also helps contribute to electrolyte balance and is required for protein synthesis.

Intake Recommended intake

EU NRV: 375mg


UK average daily intake

Requirements vary depending on age and gender. The UK National Diet and Nutrition Survey lists up-to-date intake requirements and average intakes.1


As a supplement Available as a single supplement. Also commonly available as part of a multivitamin and mineral formula.

Different multivitamin and minerals products will vary in the percentage NRVs they include. People should always check the label for information about a specific product.

Found in (dietary sources) Magnesium is present in all green plants. The main sources are unrefined cereals and wholemeal bread, green leafy vegetables, and peanuts.

Over 80 per cent of magnesium is lost in the removal of the germ and outer layers of cereal grains.

Deficiency Symptoms include loss of appetite, nausea, fatigue, weakness, insomnia, diarrhoea.

Hypocalcaemia (low calcium levels in the blood) is common in moderate to severe magnesium deficiency.

Obvious clinical signs of deficiency are uncommon.2

Precautions and contraindications Doses exceeding the Safe Upper Level are best avoided in renal (kidney) impairment.

Safe Upper Level: 400mg/day3

Use in pregnancy and breastfeeding There is no evidence of adverse effects in pregnancy and breastfeeding.
Interactions e.g. with other medications Excessive alcohol intake may increase the loss of magnesium in urine.

Loop diuretics and thiazide diuretics can increase the loss of magnesium in urine and lead to magnesium depletion.

Magnesium can reduce the absorption of the antibiotics tetracyclines, which should be taken at least two hours before or after a magnesium-containing supplement.

People taking heart medication should consult their doctor or pharmacist before taking magnesium.2, 4

Adverse effects Doses of 3–5grams have a laxative effect.
References 1.

2.     Mason, P. Dietary Supplements. Pharmaceutical Press, London, 2001.

3.     Expert Group on Vitamins and Minerals, 2003.

4.     Gaby, A. R. A-Z Guide to Drug-Herb-Vitamin Interactions. HealthNotes 2006.