In short: yes, you can take magnesium while pregnant. During pregnancy and while breastfeeding you need around 300 mg a day, the same as other women. Nuts, porridge oats, wholegrains and green vegetables can get you there easily. A supplement can close any gap, ideally up to 250 mg a day and agreed with your midwife or obstetrician. For leg cramps, magnesium helped markedly more often than a placebo in one study.
Key points
- Daily need: 300 mg of magnesium a day, the same in pregnancy and while breastfeeding. This is what the EU food safety authority EFSA and the German Nutrition Society (DGE) recommend.
- Food first: a portion of porridge oats, two slices of wholemeal bread, a handful of almonds and a plate of spinach together already add up to just over 350 mg.
- Supplements: up to 250 mg of magnesium a day from supplements is considered safe for pregnant and breastfeeding women too. Count the magnesium in your pregnancy multivitamin towards this.
- Leg cramps: in a study of 86 pregnant women, cramps halved in 86% of those taking magnesium, compared with 61% on placebo.
- Check with your team: agree every dose with your midwife or obstetrician, especially above 250 mg or if you have kidney problems.
Contents
- Do pregnant women need more magnesium?
- How much magnesium in pregnancy?
- 400 or 800 mg magnesium: is that too much?
- Which magnesium is best in pregnancy?
- Getting to 300 mg through food
- Does magnesium help with leg cramps in pregnancy?
- Magnesium in the second trimester and late pregnancy
- Can you take magnesium while breastfeeding?
- Magnesium in hospital: what about the infusion?
- Magnesium tablets and pregnancy outcomes: what has been studied?
- When to be careful
- Frequently asked questions
- Limits of the research and all sources
Do pregnant women need more magnesium?
No, your need barely rises. For pregnant and breastfeeding women, 300 mg of magnesium a day applies, the same figure as for other adult women. What matters is that you actually reach this amount during this time.
Your body still has plenty to do with magnesium, though. Magnesium has a role in the process of cell division. Magnesium contributes to normal protein synthesis. Both are in full swing during pregnancy, in you and in your baby.
What the studies show: EFSA found no evidence of a higher need in pregnancy and while breastfeeding, and therefore sets the same figure as for other women.1 The DGE also arrived at 300 mg in 2021.2 A full-term baby contains only around 0.8 g of magnesium in total.3 Spread across roughly 280 days of pregnancy, that works out to about 3 mg a day on average (our calculation). In Germany's National Nutrition Survey, though, almost one in three women (29%) fell short of the reference value.4
How much magnesium in pregnancy?
300 mg a day in total, from food, drinks and a supplement if needed, combined. From supplements, you shouldn't take more than 250 mg a day unless your obstetrician says otherwise. This upper limit applies explicitly to pregnant and breastfeeding women too.
| What | Amount per day | Source |
|---|---|---|
| Need in pregnancy | 300 mg | EFSA, DGE1, 2 |
| Need while breastfeeding | 300 mg | EFSA, DGE1, 2 |
| Upper limit from supplements, magnesium-enriched water and fortified foods | 250 mg | EFSA5 |
| Magnesium from ordinary food | no upper limit | EFSA5 |
The 250 mg limit applies to magnesium from tablets, powders and effervescent tablets. Magnesium from nuts, bread or vegetables doesn't count towards it. You can safely take in as much magnesium from food as it provides.
What the studies show: EFSA set the upper limit of 250 mg for adults, including pregnant and breastfeeding women. The reason is possible digestive complaints such as loose stools at higher amounts.5 You can find the figures for all age groups in How much magnesium per day?
How to do it: many pregnancy multivitamins already contain magnesium. Check the nutrition label and add it up:
- Worked example: multivitamin with 100 mg magnesium + magnesium supplement with 150 mg = 250 mg → right at the limit.
- Multivitamin with 100 mg + magnesium supplement with 300 mg = 400 mg → above the upper limit. Only take this much if your obstetrician specifically recommends it.
Bring your list to your next antenatal appointment and ask your midwife or obstetrician whether the total is right for you.
400 or 800 mg magnesium: is that too much?
For taking on your own, yes: 400 or 800 mg is above the 250 mg upper limit from supplements. If your obstetrician recommends an amount like this, for example because of leg cramps, that's a medical decision made specifically for you. In that case, follow their advice.
Also check what the figure on the pack actually means. "400 mg" can refer to the elemental magnesium or to the whole compound. 400 mg of magnesium citrate, for example, contains considerably less than 400 mg of magnesium. What counts towards the upper limit is always the amount of magnesium given in the nutrition table.
What the studies show: the studies on leg cramps in pregnancy used 300 to 360 mg a day.8, 21 More magnesium mainly brings a higher risk of diarrhoea, because what the gut doesn't absorb binds water.5
Which magnesium is best in pregnancy?
Organic forms such as magnesium citrate or magnesium bisglycinate are a good choice. They are absorbed better than magnesium oxide. Bisglycinate is also considered especially gentle on the stomach, which can be welcome if you have pregnancy nausea. Take your supplement with a meal and split larger amounts into two doses.
What the studies show: a systematic review of 14 comparative studies found that organic forms are absorbed better than inorganic ones such as oxide.6 The studies in pregnant women used magnesium bisglycinate, magnesium citrate and magnesium lactate.8, 21, 22 You can compare all the forms in Which magnesium is best?
Tip: taking iron during pregnancy? Take your magnesium at a different meal, with about two hours in between. That way the two don't interfere with each other's absorption. More on this in Combining magnesium.
Getting to 300 mg through food
With a few fixed building blocks each day, you can usually meet your needs without a supplement. The best sources are seeds, nuts, porridge oats, wholegrains, pulses and dark green vegetables.
| Food | Portion | Magnesium |
|---|---|---|
| Porridge oats | 50 g | 69 mg |
| Wholemeal bread | 2 slices (100 g) | 75 mg |
| Almonds | 30 g (a handful) | 81 mg |
| Spinach, cooked | 150 g | 131 mg |
| Together | 356 mg |
Values from the US nutrient database USDA FoodData Central,7 portions and total are our calculation.
Pumpkin seeds are especially rich: 30 g provides around 178 mg.7 More examples and the full table are in Magnesium-rich foods.
What the studies show: a review on magnesium in pregnancy advises pregnant women to eat more magnesium-rich foods such as nuts, seeds, beans and leafy greens, and to supplement in a safe amount if needed.11
Does magnesium help with leg cramps in pregnancy?
It can be worth a try. Leg cramps are common in pregnancy, especially at night and in the second half.10 In one controlled study, they eased markedly more often with magnesium than with placebo. Talk to your midwife or obstetrician beforehand about which amount is right for you.
Magnesium contributes to normal muscle function. Magnesium contributes to electrolyte balance.
What the studies show: in a study from Thailand, 86 pregnant women with at least two cramps a week took magnesium bisglycinate (300 mg a day) or placebo for four weeks. With magnesium, cramps halved in 86% of the women, compared with 61% on placebo. The severity of cramps also eased markedly more often, and side effects were no more common than with placebo.8 In a Swedish study of 73 women, symptoms also eased more with magnesium than with placebo.9
Our take: two controlled studies suggest magnesium helps with leg cramps in pregnancy, and it was well tolerated in them. The Cochrane review that pools all the studies rates the results as inconsistent.10 If cramps are troubling you, you can try magnesium for four weeks after checking with your midwife or obstetrician, and see whether it helps you. Which form and amount works best is something larger studies still need to show.
With an acute cramp, it usually helps to pull your toes towards you or gently stretch your calf against a wall. If cramps come very often, or if one leg is swollen, red or warm, get that checked by a doctor soon.
Magnesium in the second trimester and late pregnancy
Your need stays at 300 mg throughout pregnancy.1, 2 So you don't need to change the amount by trimester. Leg cramps become more common in the second and third trimesters, which is why many women ask about magnesium around then.
Some people hear that you should stop magnesium in the final weeks because it might slow down labour. We found no evidence that magnesium tablets delay birth. In studies that used magnesium after preterm contractions to try to prevent early birth, there was no difference.16 Whether to keep taking it up to delivery is best discussed with your midwife.
What the studies show: the leg cramp studies included women between 14 and 36 weeks of pregnancy.8, 10 The baby stores most of its minerals in the final third of pregnancy.3
Can you take magnesium while breastfeeding?
You also need 300 mg a day while breastfeeding.1, 2 Your milk reliably gets its magnesium, even if you sometimes eat less. So a supplement is for you, not for the milk. The same 250 mg upper limit from supplements applies here.5 Talk to your midwife or doctor before supplementing while breastfeeding too.
What the studies show: breast milk contains an average of around 31 mg of magnesium per litre. How much magnesium goes into the milk depends barely at all on the mother's diet or supplements.12 Fully breastfed babies drink around 0.8 litres a day.13 That's about 25 mg of magnesium your body supplies for the milk each day (our calculation).
Magnesium in hospital: what about the infusion?
You may have heard that pregnant women sometimes get magnesium through a vein in hospital. That's a medical treatment with magnesium sulfate, given in a much higher amount and under monitoring. It has nothing to do with magnesium tablets from a shop or pharmacy.
The infusion is used mainly in two situations:
- With severe pre-eclampsia (a form of high blood pressure in pregnancy), to prevent seizures.
- Before a very early birth, to protect the baby's brain.
What the studies show: in six studies with over 11,000 women with pre-eclampsia, magnesium sulfate cut the risk of seizures (eclampsia) by more than half. A quarter of the women noticed side effects, mostly hot flushes.14 When birth threatened before 34 weeks, babies were less likely to develop cerebral palsy, a movement disorder caused by early brain injury, after magnesium sulfate.15 These results apply to medical treatment in hospital. Nothing can be concluded from them for supplements.
Magnesium tablets and pregnancy outcomes: what has been studied?
Researchers have also studied whether magnesium tablets affect how pregnancy progresses. The results are mixed. No recommendation to take magnesium can be drawn from them, but they are worth knowing if you read about the topic.
What the studies show: a Cochrane review of 10 studies with 9,090 women found that pregnant women on magnesium needed hospital admission less often.17 An analysis of seven studies found pre-eclampsia was less common with magnesium, but only in studies that also included higher-risk pregnancies. In women without a particular risk, there was no clear difference.18
When to be careful
Magnesium from food is not a concern in pregnancy. With supplements, the most common side effect is loose stools, especially with larger amounts taken at once. This can usually be avoided by splitting the amount across two meals.
Important: if your kidney function is reduced, magnesium can build up in your body.19 In that case, only take magnesium if your doctor prescribes it. With iron, thyroid hormone and certain antibiotics, you need a gap of a few hours. The details are in When should you take magnesium? If you're prescribed magnesium as a medicine, it counts towards your daily total. Check before adding any extra supplement.
Frequently asked questions
Can you take magnesium while pregnant? Yes. Up to 250 mg of magnesium a day from supplements is considered safe in pregnancy too.5 Still talk to your midwife or obstetrician about taking it, especially if you're already taking a multivitamin that contains magnesium.
How much magnesium a day in pregnancy? 300 mg a day in total from food and drinks, of which no more than 250 mg from supplements.1, 2, 5 More only on medical advice.
Which magnesium is best in pregnancy? Organic forms such as magnesium citrate or magnesium bisglycinate. They're absorbed well,6 and bisglycinate is considered especially gentle on the stomach. The study with the clearest result for leg cramps used bisglycinate.8
What is magnesium good for in pregnancy? Magnesium has a role in the process of cell division. Magnesium contributes to normal muscle function. Magnesium contributes to a reduction of tiredness and fatigue. Magnesium contributes to the maintenance of normal bones. More on this in Magnesium: what it does in the body.
Can you take too much magnesium in pregnancy? Hardly, from food. With supplements above 250 mg a day, the main risk that rises is diarrhoea.5 With healthy kidneys, the body excretes any excess magnesium.19
Do you need more magnesium while breastfeeding? No, 300 mg a day applies then too.1, 2 Your milk gets its magnesium largely regardless of whether you supplement.12
Limits of the research and all sources
Whether pregnant women need more magnesium isn't seen the same way by everyone: EFSA found no evidence of a higher need,1 while a review takes the view that need is higher and that many pregnant women don't meet it.11 Magnesium status can only be measured imprecisely in blood, which makes such questions hard to answer.11
For leg cramps, there are only a few small studies that measure their results differently. The Cochrane review (8 studies, 576 women) therefore couldn't pool them and rates the strength of evidence as low.10 In a Norwegian study of 38 women, cramps didn't ease more with 360 mg of magnesium lactate and citrate than with placebo.21 The same applied in a Brazilian study of 132 women using magnesium citrate.22 An analysis of four studies with 332 women found no overall difference in frequency.23 Even in the positive studies, cramps eased noticeably with placebo too.8
On pregnancy outcomes, the Cochrane review concludes there aren't enough high-quality studies to show a benefit from magnesium tablets. In the two best studies, there were no differences in the main outcomes.17 A large study of 829 higher-risk pregnant women found no difference in complications for mother or baby with 300 mg of magnesium citrate.20 After preterm contractions, maintenance treatment with magnesium didn't prevent preterm birth, while diarrhoea was more common.16 The hospital findings on magnesium sulfate come from medical treatment at a high dose and don't carry over to supplements.14, 15 The figures for breast milk vary considerably between studies.12
Show all 23 sources
| # | Study | Who was studied | Result | Strength of evidence |
|---|---|---|---|---|
| 1 | EFSA NDA Panel 2015, EFSA Journal | dietary surveys from 9 EU countries | women 300 mg; no higher need in pregnancy and while breastfeeding | official assessment |
| 2 | DGE, ÖGE, SGE 2021: reference values for magnesium | estimates | pregnant women 300 mg, breastfeeding women 300 mg | official reference values |
| 3 | Kovacs 2016, Physiol Rev | review of mineral metabolism | full-term newborn contains around 0.8 g magnesium; most minerals stored in the final third | review |
| 4 | Max Rubner Institute 2008: National Nutrition Survey II, Part 2 | 15,371 respondents (14 to 80 years) | 29% of women below the reference value | nationwide survey |
| 5 | EFSA / SCF 2001 | scientific opinion | upper limit of 250 mg/day from supplements, also for pregnant and breastfeeding women | official assessment |
| 6 | Pardo et al. 2021, Nutrition | 14 comparative studies | organic forms absorbed better than inorganic | systematic review |
| 7 | USDA FoodData Central, SR Legacy | nutrient database | magnesium content per 100 g | reference data |
| 8 | Supakatisant & Phupong 2015, Matern Child Nutr | 86 pregnant women (14 to 34 weeks), magnesium bisglycinate chelate 300 mg/day, 4 weeks | cramps halved in 86% vs. 61% (placebo); side effects equal | controlled study, university (Thailand) |
| 9 | Dahle et al. 1995, Am J Obstet Gynecol | 73 pregnant women, 3 weeks | fewer cramp-related symptoms than with placebo | small controlled study, university (Sweden) |
| 10 | Luo et al. 2020, Cochrane Database Syst Rev | 8 studies, 576 pregnant women | magnesium for leg cramps: inconsistent results; side effects like placebo | Cochrane review, low certainty for individual studies |
| 11 | Dalton et al. 2016, Nutr Rev | review | advises magnesium-rich foods or safe supplementation; sees a higher need | review |
| 12 | Dórea 2000, J Am Coll Nutr | review of breast milk analyses | median 31 mg/l; barely depends on the mother's diet and supplements | review |
| 13 | Daniels et al. 2019, Am J Clin Nutr | 113 mother-infant pairs (Indonesia) | fully breastfed babies drank an average of 787 ml of milk a day | cross-sectional study |
| 14 | Duley et al. 2010, Cochrane Database Syst Rev | 6 studies, 11,444 women with pre-eclampsia | magnesium sulfate (hospital): eclampsia risk more than halved; 24% side effects | Cochrane review, medical treatment |
| 15 | Shepherd et al. 2024, Cochrane Database Syst Rev | 6 studies, 5,917 women with threatened preterm birth before 34 weeks | magnesium sulfate (hospital): less cerebral palsy in the child | Cochrane review, medical treatment |
| 16 | Han et al. 2013, Cochrane Database Syst Rev | 4 studies, 422 women after preterm contractions | magnesium maintenance treatment: no difference in preterm births; more diarrhoea | Cochrane review |
| 17 | Makrides et al. 2014, Cochrane Database Syst Rev | 10 studies, 9,090 pregnant women | fewer hospital admissions; main outcomes unchanged in the best studies | Cochrane review |
| 18 | Yuan et al. 2021, Biol Trace Elem Res | 7 studies, 2,653 pregnant women | pre-eclampsia less common overall; no clear difference in women without risk | meta-analysis |
| 19 | Rosner et al. 2023, Mayo Clin Proc | review | build-up when kidney function is reduced | review |
| 20 | de Araújo et al. 2020 (BRAMAG), BMC Pregnancy Childbirth | 829 higher-risk pregnant women, magnesium citrate 300 mg until birth | no difference in complications for mother and baby | large controlled study |
| 21 | Nygaard et al. 2008, Eur J Obstet Gynecol Reprod Biol | 38 pregnant women, 360 mg magnesium lactate/citrate, 2 weeks | no difference from placebo for leg cramps | small controlled study |
| 22 | de Araújo et al. 2020, PLoS ONE | 132 pregnant women, magnesium citrate 300 mg/day, 4 weeks | no difference from placebo for leg cramps | controlled study |
| 23 | Liu et al. 2021, Taiwan J Obstet Gynecol | 4 studies, 332 pregnant women | no overall reduction in cramp frequency | meta-analysis |
Author: PRONESIUM Editorial Team · Last reviewed: 01/10/2026 · This article does not replace medical advice or advice from your midwife.
