Last updated: October 2026
Magnesium is generally considered safe in pregnancy at normal amounts, and most women can get the 270mg a day they need from food. But a Cochrane review found not enough good evidence that magnesium supplements help in pregnancy, including for leg cramps. The NHS recommends only folic acid and vitamin D. Ask your midwife or GP before taking magnesium.
This guide covers what the evidence says, leg cramps and constipation, how much magnesium you need, magnesium-rich foods, and what to check before taking any supplement.
Is magnesium safe in pregnancy?
Magnesium from food is safe and important: it contributes to normal muscle function, the maintenance of normal bones and teeth, and the reduction of tiredness and fatigue. Low-dose magnesium supplements are also generally considered safe in pregnancy, and many pregnancy multivitamins contain some.
Still, check with your midwife, GP or pharmacist before you start, especially if you have kidney problems, take other medicines or supplements, or have been told you have high blood pressure.
What the NHS recommends
| Supplement | NHS advice in pregnancy |
|---|---|
| Folic acid | 400 micrograms a day, ideally from 3 months before pregnancy until 12 weeks |
| Vitamin D | 10 micrograms a day, especially from October to March |
| Vitamin A (retinol) | Avoid supplements containing it, and liver products |
| Magnesium | Not routinely recommended; get it from a balanced diet |
What the research shows
A 2014 Cochrane review of magnesium supplements in pregnancy, covering 10 trials and over 9,000 women, concluded there isn’t enough high-quality evidence to show they’re beneficial. Some older trials hinted at fewer complications, but they were small or poorly designed.
Claims online that magnesium prevents premature birth, pre-eclampsia or problems for the baby later in life come from observational studies or animal research, not from good trials of supplements.
Magnesium for leg cramps in pregnancy
Leg cramps are common, especially at night in the second and third trimesters. A 2020 Cochrane review found the evidence for magnesium was inconsistent and low certainty: one trial found more women became cramp-free, while others found little or no difference.
What the NHS suggests instead:
- gentle regular exercise, especially ankle and leg movements
- pulling your toes up towards your ankle and rubbing the muscle when a cramp starts
- stretching your calves before bed
If one leg is swollen, red, warm or painful (not just cramping), contact your midwife or GP urgently, as it could be a blood clot. See also magnesium for cramps.
Magnesium and pregnancy constipation
Constipation is common in pregnancy. Start with more fibre, fluids and gentle activity. Some magnesium-based laxatives are used in pregnancy, but only take one if a pharmacist, midwife or GP recommends it. Iron supplements often make constipation worse, so mention it if you’re taking iron.
How much magnesium do you need?
- During pregnancy: about 270mg a day, the same as other adult women in UK guidance.
- While breastfeeding: about 50mg a day more.
- From supplements: only the amount your midwife or GP agrees. Check your pregnancy multivitamin first, as it may already contain magnesium.
Too much magnesium from supplements mainly causes diarrhoea, which can lead to dehydration in pregnancy.
Magnesium-rich foods for pregnancy
| Food | Why it helps |
|---|---|
| Pumpkin and sunflower seeds | One of the richest sources |
| Almonds, cashews, peanut butter | Easy snacks |
| Spinach, kale and other greens | Also provide folate |
| Wholegrain bread, oats, brown rice | Also help with constipation |
| Beans, lentils, chickpeas | Also provide iron and fibre |
| Bananas, avocado, dark chocolate | Smaller amounts |
Magnesium and pre-eclampsia
You may read that magnesium is “used for pre-eclampsia”. That’s magnesium sulphate given by drip in hospital to prevent seizures in women with severe pre-eclampsia. It’s a medical treatment, not something oral supplements can replace. If you notice a severe headache, vision problems, pain below the ribs or sudden swelling of your face, hands or feet, contact your midwife or maternity unit straight away.
Can I take Evopure products while pregnant?
We don’t recommend our products during pregnancy or breastfeeding. Our Magnesium Glycinate Sleep Complex contains herbal extracts that haven’t been studied enough in pregnancy, and CBD isn’t advised in pregnancy. See CBD in pregnancy. For general magnesium information, see magnesium for women.
FAQs
Can I take magnesium while pregnant?
Low-dose magnesium is generally considered safe in pregnancy, but it isn’t routinely recommended. Ask your midwife or GP first, and check whether your pregnancy multivitamin already contains it.
Does magnesium help leg cramps in pregnancy?
The evidence is inconsistent. One trial found a benefit, others didn’t. Stretching and gentle exercise are the first things to try.
How much magnesium do pregnant women need?
About 270mg a day, mostly from food, and about 50mg more while breastfeeding.
Which magnesium is safe in pregnancy?
There’s no evidence one form is safer. Use only the product and amount your midwife, GP or pharmacist agrees, and avoid blends with herbal extracts.
Does magnesium prevent pre-eclampsia?
There’s no good evidence that oral magnesium supplements prevent it. Magnesium sulphate by drip is a hospital treatment for severe pre-eclampsia.
Can I use Epsom salt baths when pregnant?
A warm, not hot, Epsom salt bath is usually fine, but check with your midwife. Very little magnesium is absorbed through the skin.
Sources
- NHS. Pregnancy vitamins and supplements.
- NHS. Common health problems in pregnancy.
- NHS. Vitamins and minerals: magnesium.
- Makrides M et al. Magnesium supplementation in pregnancy. Cochrane Database Syst Rev, 2014.
- Luo L et al. Interventions for leg cramps in pregnancy. Cochrane Database Syst Rev, 2020.
This guide is general information. Always follow the advice of your midwife or GP.
