Magnesium

Your body needs magnesium for more than 300 chemical reactions, from muscle contraction to nerve signalling, energy production and protein building.^[1] About 60% of the magnesium you carry sits in your bones. It is one of the most widely studied minerals in nutrition. It is also one women run low on most often.

If you have been told to take magnesium for cramps, sleep or a rough luteal phase, this page goes into which form actually works, how much you need and what the research shows.

Forms of magnesium

Magnesium is used in supplements in several chemical forms. They differ meaningfully in how well your body absorbs them. This is measured as bioavailability.

Magnesium oxide is the most common form used in supplements because it is inexpensive to produce. It also has the lowest bioavailability. A large fraction of the dose passes through the gastrointestinal tract without being absorbed, which is why magnesium oxide is often used at high doses for constipation rather than for raising magnesium status.^[1]

Magnesium citrate is magnesium bound to citric acid. It is well absorbed and is the form used in most clinical research on dysmenorrhea.^[1]

Magnesium bisglycinate (also called magnesium glycinate) is magnesium bound to two molecules of the amino acid glycine. It is absorbed efficiently and tends to be well tolerated digestively.^[1]

Magnesium L-threonate is a newer form developed for its ability to cross the blood-brain barrier in animal studies. It is marketed for cognitive support, but the human evidence base is small and most published trials are funded by manufacturers. Independent replication is still limited.

Magnesium chloride is most often used topically, as magnesium oil or bath flakes. Claims about transdermal absorption are common in marketing but are not well supported by controlled clinical research. For raising magnesium status, oral forms remain the better-evidenced approach.

How much you need

The European Food Safety Authority recommends 300 mg of magnesium per day for adult women. Your needs rise during pregnancy and breastfeeding.^[2]

Most women in Europe do not reach that from food alone.^[1] Low-magnesium diets, high stress, heavy alcohol and certain medications all reduce how much your body gets or keeps. That includes proton pump inhibitors for reflux and some diuretics.^[1]

The science on women's health

Period pain

A 2020 systematic review and meta-analysis looked at 16 clinical trials on micronutrients for period pain. The authors found that magnesium, alongside calcium, zinc and several vitamins, contributed to pain relief in primary dysmenorrhea. They noted the research base is still smaller than it should be.^[3]

More recently, researchers tested 200 mg of magnesium citrate per day in 172 women with painful periods over three cycles. Pain scores dropped and painkiller use reduced, compared to where the women started. A combined oral contraceptive worked more strongly in the same study, but magnesium still produced a real effect.^[4]

The biology fits. Magnesium relaxes the smooth muscle of your uterus and lowers the prostaglandins that drive cramping.^[4] The research points to at least three cycles before you can judge whether it works for you.

PMS

The evidence here is weaker than the hype suggests.

Researchers looked at 31 clinical trials in more than 3,000 women of reproductive age, focused on the emotional side of PMS: mood swings, irritability, low mood. Vitamin B6, calcium and zinc had the strongest evidence. For magnesium on its own, the evidence was not strong enough for a clear conclusion. The review was published in Nutrition Reviews in 2025.^[5]

Older studies and clinical practice suggest magnesium helps, especially when combined with vitamin B6. The gold-standard research is still catching up. Women's health research has been underfunded for decades. This is one of the areas showing the cost of that.

EU authorised health claims

Under EU law, magnesium is officially authorised to carry the following health claims:

• Magnesium contributes to a reduction of tiredness and fatigue
• Magnesium contributes to normal energy-yielding metabolism
• Magnesium contributes to normal functioning of the nervous system
• Magnesium contributes to normal muscle function
• Magnesium contributes to normal protein synthesis
• Magnesium contributes to normal psychological function
• Magnesium contributes to the maintenance of normal bones and teeth
• Magnesium contributes to electrolyte balance
• Magnesium has a role in the process of cell division^[2]

References

[1] National Institutes of Health, Office of Dietary Supplements. Magnesium: Fact Sheet for Health Professionals. ods.od.nih.gov/factsheets/Magnesium-HealthProfessional

[2] Commission Regulation (EU) No 432/2012 establishing a list of permitted health claims made on foods. Official Journal of the European Union, 25 May 2012. eur-lex.europa.eu

[3] Saei Ghare Naz M, Kiani Z, Rashidi Fakari F, et al. The effect of micronutrients on pain management of primary dysmenorrhea: a systematic review and meta-analysis. Journal of Caring Sciences 2020;9(1):47-56. doi.org/10.34172/jcs.2020.008

[4] Gök S, Gök B. Investigation of laboratory and clinical features of primary dysmenorrhea: comparison of magnesium and oral contraceptives in treatment. Cureus 2022;14(11):e32028. doi.org/10.7759/cureus.32028

[5] Robinson J, Ferreira A, Iacovou M, Kellow NJ. Effect of nutritional interventions on the psychological symptoms of premenstrual syndrome in women of reproductive age: a systematic review of randomized controlled trials. Nutrition Reviews 2025;83(2):280-306. doi.org/10.1093/nutrit/nuae043