How much magnesium per day, by age and sex

1. 01

   Adult men: 400-420 mg/day

   The RDA for men is 400 mg/day at ages 19-30 and 420 mg/day at 31 and older (NIH ODS; IOM 1997). This is the intake that meets the needs of 97-98% of healthy men. Most men fall short from food alone because refined grains displace the seeds, greens, and legumes that carry magnesium. Hitting it takes deliberate sources: 1 oz pumpkin seeds (156 mg) plus 1 cup cooked spinach (157 mg) plus 1 cup black beans (120 mg) already clears 420 mg.

2. 02

   Adult women: 310-320 mg/day

   The RDA for women is 310 mg/day at ages 19-30 and 320 mg/day at 31 and older (NIH ODS). Pregnancy raises it to ~350-360 mg/day; lactation is ~310-320 mg/day. The lower female requirement reflects lower average body and muscle mass, not a different mechanism. Women fall short from food at similar rates to men (NHANES), so the same seed, green, and legume sources apply.

3. 03

   The 350 mg upper limit applies only to supplements

   The tolerable upper limit (UL) for magnesium is 350 mg/day, but this applies only to supplemental magnesium, not to magnesium from food (NIH ODS). Food magnesium has no UL because the gut down-regulates fractional absorption as intake rises, so excess is simply not absorbed. The supplemental cap exists because high doses of poorly absorbed forms, especially magnesium oxide, draw water into the bowel and cause osmotic diarrhea. This is why a 500 mg food day is fine but a 500 mg oxide tablet is not.

4. 04

   Adolescents and older adults

   Teen boys 14-18 need 410 mg/day and teen girls 360 mg/day (NIH ODS), reflecting the growth spurt. Requirements do not fall with age, but absorption declines and some medications (proton pump inhibitors, certain diuretics) lower magnesium status in older adults, so the older population is at higher risk of falling short despite an unchanged RDA. The 31-and-older numbers (420 mg men, 320 mg women) hold through later life.

5. 05

   Cover the RDA from food first

   Food is the preferred route because magnesium arrives packaged with fiber, potassium, and protein, and carries no upper limit. The densest everyday sources are pumpkin seeds (156 mg/oz), cooked spinach (157 mg/cup), black beans (120 mg/cup), cooked quinoa (118 mg/cup), and almonds (80 mg/oz), per USDA FoodData Central. Stacking three of these clears more than half the daily target before any pill. See our magnesium-rich foods ranking for the full mg-per-serving table.

6. 06

   Supplement only the gap, and pick the right form

   If you reliably eat seeds, greens, and legumes you likely clear the RDA from food and need no pill. When a gap exists, a typical supplemental dose is 100-200 mg/day, which stays under the 350 mg UL with room for dietary magnesium on top. Form matters: glycinate and citrate are far better absorbed and gentler than the cheap, common oxide, which is mostly excreted and causes the most diarrhea (Walker et al. 2003). See our breakdown of magnesium forms for the full comparison.

7. 07

   Signs you may be falling short

   Serum magnesium reflects under 1% of total body stores, so a normal blood test does not rule out a deficit (Workinger et al. 2018). Frank deficiency is uncommon in healthy people but more likely with high alcohol intake, GI malabsorption, type 2 diabetes, or long-term PPI or diuretic use. Early signs are non-specific: muscle cramps, fatigue, and poor sleep. Rather than chase symptoms, the reliable move is to ensure the diet hits the RDA from the food sources above.

What people ask us next.

Q01

How much magnesium should I take per day?

The RDA is 400-420 mg/day for adult men and 310-320 mg/day for adult women (NIH Office of Dietary Supplements). Pregnancy raises it to ~350-360 mg/day. That total can and ideally should come mostly from food. If you supplement, a typical dose is 100-200 mg/day, kept under the 350 mg/day supplemental upper limit, with dietary magnesium making up the rest.

Q02

Is 500 mg of magnesium per day too much?

It depends on the source. 500 mg/day from food is fine and carries no upper limit, because the gut self-limits absorption as intake rises (NIH ODS). A 500 mg supplement is above the 350 mg/day supplemental upper limit and risks osmotic diarrhea, especially with poorly absorbed magnesium oxide. The cap applies only to supplemental magnesium, not to magnesium from food.

Q03

How much magnesium per day for a woman?

310 mg/day for women aged 19-30 and 320 mg/day for women 31 and older (NIH ODS). Pregnancy raises it to ~350-360 mg/day and lactation is ~310-320 mg/day. Most of that should come from food; supplement only the measured gap, and stay under the 350 mg/day supplemental upper limit.

Q04

Can I get enough magnesium from food alone?

Yes, for most people. A day with 1 oz pumpkin seeds (156 mg), 1 cup cooked spinach (157 mg), and 1 cup black beans (120 mg) already exceeds 430 mg (USDA FoodData Central). The reason ~48% of Americans fall short is refined carbohydrates, which displace the seeds, greens, legumes, and whole grains that carry magnesium (NHANES, Moshfegh 2009).

Q05

What happens if I take too much magnesium?

From food, nothing: the gut down-regulates absorption and the excess is not absorbed. From supplements above the 350 mg/day upper limit, the main effect is osmotic diarrhea, cramping, and nausea, worst with magnesium oxide (NIH ODS). True magnesium toxicity (hypermagnesemia) is rare and occurs mainly in people with impaired kidney function, who should not supplement without medical advice.

Q06

Which magnesium form is best for daily use?

Glycinate and citrate are the best-tolerated, best-absorbed everyday forms; oxide is the cheapest but mostly excreted and the most likely to cause diarrhea (Walker et al. 2003). Glycinate is gentle and good for general use and sleep; citrate is well absorbed and mildly laxative, useful if constipation is also a concern. See our full magnesium forms comparison for the ranking.