Pregnancy Supplements: Magnesium

Magnesium is an essential mineral that your body needs for normal functions, including releasing energy from food and supporting bone health. You can find it naturally in foods such as spinach, nuts and wholemeal bread.

If you are wondering whether you should take a magnesium supplement during pregnancy, the key point is that UK pregnancy guidance does not recommend routine magnesium supplements for everyone. The NHS specifically recommends folic acid and vitamin D during pregnancy, while a varied, balanced diet should provide most other vitamins and minerals.

That does not mean magnesium supplements are never appropriate. Individual circumstances vary, so if you are considering one during pregnancy, your midwife, GP or pharmacist can help you decide whether it is suitable for you.

What does magnesium do in the body?

Magnesium is involved in many normal processes in the body.

According to the NHS, magnesium helps turn the food we eat into energy. It also helps the parathyroid glands work normally. These glands produce hormones that are important for bone health.

Magnesium is present in a wide range of everyday foods, which is one reason most people can meet their needs through their diet.

Do you need more magnesium during pregnancy?

It is easy to assume that pregnancy automatically means adding several supplements, but current UK guidance is more specific.

The NHS pregnancy supplement guidance recommends folic acid and vitamin D, with iron supplements recommended if blood tests show that iron levels are low. Magnesium is not listed as a routine pregnancy supplement.

The NHS also advises that most vitamins and minerals can be obtained through a healthy, varied diet during pregnancy.

If you have been advised to take magnesium for a particular medical reason, that is different from routinely taking a supplement. Follow the advice given by your healthcare professional rather than using general supplement guidance to decide how much to take.

Which foods contain magnesium?

Magnesium occurs naturally in many foods.

The NHS lists good sources including:

spinach
nuts
wholemeal bread

A varied diet containing wholegrains, vegetables, nuts and other nutrient-rich foods can contribute to your magnesium intake alongside many other vitamins and minerals.

Food preferences, allergies, intolerances, cultural diets and access to particular foods differ. If you are worried that your diet may not provide what you need during pregnancy, speak to your midwife, GP or a registered dietitian rather than feeling that you have to manage it alone.

Should you take a magnesium supplement during pregnancy?

There is no general NHS recommendation for every pregnant person to take a magnesium supplement.

This is an important distinction because magnesium is often marketed alongside claims about pregnancy symptoms. A supplement being widely available does not mean that it is routinely needed or suitable for every pregnancy.

NICE specifically advises against recommending magnesium supplements solely to prevent hypertensive disorders during pregnancy, including pre-eclampsia.

If you want to take magnesium for another reason, discuss it with your midwife, GP or pharmacist first. They can consider your health, diet, medicines and any other supplements you already take.

Can magnesium supplements help with pregnancy symptoms?

You may see magnesium supplements promoted for concerns such as leg cramps, sleep problems, headaches or other pregnancy symptoms.

These symptoms can have different causes, and taking magnesium without knowing the cause may not be appropriate. Current NHS pregnancy guidance does not recommend magnesium as a routine supplement for managing pregnancy symptoms.

If a symptom is persistent, new, painful or worrying you, speak to your maternity team. They can help assess what is happening and advise you based on your individual circumstances.

This is particularly important because symptoms that seem ordinary can sometimes need medical assessment during pregnancy.

Can you take too much magnesium?

Yes. Supplements can provide much larger amounts of magnesium than you would normally obtain from food.

The NHS states that taking high doses of magnesium supplements, more than 400 mg, for a short period can cause diarrhoea. It also says there is not enough evidence to know the effects of taking high doses for a long time.

Department of Health and Social Care advice, as summarised by the NHS, is that people should be able to obtain the magnesium they need from a varied and balanced diet. The NHS says that 400 mg or less a day from magnesium supplements is unlikely to cause harm for most people.

That figure is an upper supplementary amount in general adult guidance, not a recommended pregnancy dose. It should not be used as a target for supplementation during pregnancy.

If a healthcare professional has advised magnesium for a medical reason, follow their individual instructions.

What about magnesium in a prenatal multivitamin?

Pregnancy multivitamins contain different combinations and amounts of nutrients. Some may contain magnesium alongside folic acid, vitamin D and other vitamins or minerals.

Check the label before combining supplements so you know what you are already taking.

The NHS also advises avoiding cod liver oil and supplements containing vitamin A in the form of retinol during pregnancy because too much vitamin A can harm a baby’s development.

If you are unsure about a prenatal vitamin or want to add a separate magnesium product, show the packaging to a pharmacist, midwife or GP. They can help you check the ingredients and whether the product is appropriate.

Magnesium supplements and magnesium sulfate are not the same thing

You may also hear about magnesium sulfate during pregnancy. This is a medicine used by maternity teams in specific clinical situations and should not be confused with an over-the-counter magnesium dietary supplement.

For example, NICE recommends intravenous magnesium sulfate in certain circumstances involving imminent preterm birth to help protect the baby’s brain. It is also used in hospital care for eclampsia and severe pre-eclampsia in particular circumstances.

These are medical treatments given and monitored by healthcare professionals. Taking an oral magnesium supplement yourself is not an alternative to these treatments and should not be used to try to prevent pregnancy complications.

When to get professional advice

Speak to your midwife, GP or pharmacist before starting a magnesium supplement during pregnancy if you are unsure whether you need one, particularly if you take medicines, have a health condition or already use a prenatal multivitamin or other supplements.

If you are considering magnesium because of a pregnancy symptom, ask your maternity team about the symptom itself rather than relying on a supplement to treat it.

Contact your maternity unit or another appropriate healthcare professional promptly if you develop symptoms during pregnancy that are severe, worsening or concerning. NHS 111 can provide urgent medical advice when you are unsure where to get help, and you should call 999 for a life-threatening emergency.

If a healthcare professional has prescribed or recommended magnesium for a specific reason, follow their advice rather than changing the amount or stopping it based on general information online.