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Magnesium for women: how much you need and when to ask a doctor

An adult woman needs 310 to 320 mg of magnesium a day, counting food and supplements. What is known about magnesium in the cycle, menopause and pregnancy, and when to ask a doctor.

How much magnesium you need

According to the NIH consumer fact sheet, the recommended intake for adult women is 310 to 320 mg of magnesium a day, 350 to 360 mg in pregnancy and 310 to 320 mg while breastfeeding. That's the total from food and supplements together.

The upper safety limit for magnesium from supplements is 350 mg a day for adults, unless a doctor says more. Food has no such limit.

Where to get it without a supplement

Nuts, seeds, legumes, whole grains and leafy greens are common sources of magnesium. If your diet includes these foods, you may not need a supplement; ask your doctor or a dietitian before starting.

Menstrual cycle and premenstrual symptoms

Magnesium has been studied for premenstrual symptoms, but the evidence is mixed and low quality. One review says it helped with fluid retention, cravings and anxiety, while admitting some included studies were questionable. A crossover trial of 54 women in the UK found no significant effect of 200 mg a day for two months on psychological symptoms, and a meta-analysis of observational studies found no link between blood magnesium and premenstrual syndrome.

Reviews on magnesium and period cramps also exist; we couldn't verify their results, so we don't cite them.

Menopause and sleep

We haven't found solid evidence to cite on magnesium and menopause symptoms, so we don't claim it. For sleep, see the magnesium for sleep guide: the most recent trial showed a small effect in adults who slept badly.

Pregnancy and breastfeeding

Magnesium needs rise a little in pregnancy, but don't start a supplement on your own: that's for your doctor or midwife, who'll know whether your prenatal vitamin already includes it.

When to ask and what to avoid

Talk to a health professional first if you have kidney disease, are pregnant or breastfeeding, or take medication. According to the NIH, osteoporosis drugs (bisphosphonates) and some antibiotics are poorly absorbed if taken close to a magnesium supplement. At high doses, the supplement can cause diarrhea, nausea and cramps.