Most adult women need 310 to 320 mg of magnesium per day. The exact number depends on your age, and whether you’re pregnant or breastfeeding. That target includes magnesium from both food and supplements, so if your diet already covers a good portion, you may not need a high-dose pill to close the gap.
Daily Targets by Age
The National Institutes of Health sets the recommended dietary allowance (RDA) for magnesium as follows:
- Women 19 to 30: 310 mg per day
- Women 31 and older: 320 mg per day
These numbers don’t jump dramatically with age. The 10 mg increase after 30 is minor, and the recommendation stays at 320 mg through your 50s, 60s, and beyond. During pregnancy, the target rises to 350 to 360 mg depending on age, and during breastfeeding it’s 310 to 320 mg.
How Much You Likely Get From Food
Before reaching for a supplement, it helps to estimate what your diet already provides. Magnesium is concentrated in seeds, nuts, leafy greens, and whole grains. A quarter cup of pumpkin seeds delivers roughly 150 mg. A cup of cooked spinach has about 157 mg. An ounce of almonds (about 23 nuts) adds around 80 mg. Even a cup of black beans provides close to 120 mg.
If your meals regularly include a mix of these foods, you may already be hitting 200 to 250 mg from diet alone. In that case, a modest supplement of 100 to 150 mg would bridge the gap. But surveys consistently show that many women fall short, particularly those eating highly processed diets with few vegetables, nuts, or whole grains.
Supplement Doses and Safety Limits
The upper limit for supplemental magnesium (not counting food) is 350 mg per day for adults. This limit exists specifically because higher supplemental doses tend to cause diarrhea, cramping, and nausea. Magnesium from food doesn’t carry that risk because it’s absorbed more gradually.
In practice, most women do well with a supplement in the 200 to 400 mg range when their diet is low in magnesium-rich foods. If you’re just trying to fill a small dietary gap, 100 to 200 mg is often enough. Starting at a lower dose and increasing gradually helps you avoid the digestive side effects that make people quit early.
Which Form of Magnesium Matters
Not all magnesium supplements are created equal. The key difference is bioavailability, meaning how much your body actually absorbs versus what passes through undigested. Organic forms of magnesium (bound to molecules your body recognizes easily) are absorbed significantly better than inorganic forms.
- Magnesium glycinate: One of the best-absorbed forms. It’s gentle on the stomach and less likely to cause loose stools, making it a good default choice. Cleveland Clinic specifically recommends this form for muscle cramps and period pain.
- Magnesium citrate: Also well absorbed, though its absorption rate decreases as the dose gets higher. It has a mild laxative effect, which can be a benefit or a drawback depending on your situation.
- Magnesium oxide: The most common form in cheap supplements because it packs more elemental magnesium per pill. But it’s poorly absorbed. A 400 mg magnesium oxide tablet delivers far less usable magnesium than the label suggests.
If you’re comparing products, check both the form and the amount of “elemental magnesium” listed. That’s the number that counts toward your daily target.
Magnesium for Period Cramps and PMS
Small clinical studies have tested magnesium for menstrual symptoms, typically using 150 to 300 mg per day. One study found that 250 mg of magnesium combined with 40 mg of vitamin B6 reduced PMS symptoms more effectively than either alone. Magnesium glycinate is the preferred form here because of its superior absorption and its effect on muscle relaxation.
If you’re trying magnesium specifically for cramps, starting around 150 mg daily is a reasonable approach. You can increase toward 300 mg if needed. Some women take it only during the luteal phase (the two weeks before their period), while others take it consistently throughout the month.
Bone Health After Menopause
Magnesium plays a direct role in bone metabolism, and research has found that women with higher magnesium intakes tend to have greater bone mineral density. Studies also show that women with osteoporosis are more likely to have low magnesium levels in their blood. In one study of postmenopausal women with osteoporosis, taking 290 mg of magnesium citrate daily for 30 days slowed bone turnover, a marker of bone loss.
This doesn’t mean magnesium alone prevents osteoporosis, but it’s a nutrient that often gets overlooked alongside calcium and vitamin D. Meeting the 320 mg RDA becomes especially important after menopause, when bone loss accelerates.
Signs You’re Not Getting Enough
Mild magnesium deficiency is surprisingly common and easy to miss because the symptoms overlap with so many other things. The earliest signs include muscle cramps, twitching (especially around the eyes or calves), fatigue, weakness, and numbness or tingling in the hands and feet. Poor sleep and increased anxiety can also be linked to low magnesium, though these are harder to pin on a single nutrient.
Severe deficiency is rare in otherwise healthy people but can cause abnormal heart rhythms, seizures, and confusion. Normal blood magnesium levels fall between 1.46 and 2.68 mg/dL, though blood tests only capture about 1% of the body’s total magnesium since most of it is stored in bones and soft tissue. That means you can be meaningfully deficient even with a normal blood result.
Certain situations increase your risk of running low: taking hormonal birth control, drinking alcohol regularly, managing diabetes or digestive conditions, or eating a diet heavy in refined grains and low in vegetables. If any of these apply, paying closer attention to your magnesium intake is worth the effort.