How Much Magnesium per Day: RDA, Upper Limit and Food Sources

Most adults need between 310 and 420 mg of magnesium a day from everything they eat and drink. Men need 400 mg a day from age 19 and 420 mg from age 31. Women need 310 mg from age 19 and 320 mg from age 31, and a little more during pregnancy. These are the Recommended Dietary Allowances (RDAs), set by the Food and Nutrition Board of the National Academies. They count food, drinks and supplements together.

The magnesium upper limit is a separate number, and it confuses a lot of people. For anyone aged 9 or older, magnesium from supplements and medicines should stay at or below 350 mg a day. Food does not count toward that limit, because healthy kidneys clear extra magnesium from food in the urine. So someone who eats 300 mg from food and takes a 250 mg supplement is above the RDA and still within the limit.

Recommended amounts by age and life stage

The figures below come from the NIH Office of Dietary Supplements (ODS) magnesium fact sheet, which reproduces the Food and Nutrition Board tables. For babies up to 12 months, the values are Adequate Intakes rather than RDAs.

Age	Male	Female	Pregnancy	Breastfeeding
0 to 6 months	30 mg	30 mg
7 to 12 months	75 mg	75 mg
1 to 3 years	80 mg	80 mg
4 to 8 years	130 mg	130 mg
9 to 13 years	240 mg	240 mg
14 to 18 years	410 mg	360 mg	400 mg	360 mg
19 to 30 years	400 mg	310 mg	350 mg	310 mg
31 to 50 years	420 mg	320 mg	360 mg	320 mg
51 years and older	420 mg	320 mg

So the answer to “how much magnesium per day” depends on your age and sex, and on whether you are pregnant or breastfeeding. Teenage boys need the most of any group under 31, and needs rise again slightly from age 31. You can see your own magnesium RDA next to other nutrients in our nutrient RDA lookup.

The upper limit for supplements, explained

The Tolerable Upper Intake Level (UL) is the most a person can take each day without a likely risk of side effects. For magnesium, the UL applies only to supplements and to medicines that contain magnesium, such as antacids and laxatives. It is the same for men and women, and it does not change in pregnancy.

Age	Upper limit from supplements and medicines
0 to 12 months	Not established
1 to 3 years	65 mg
4 to 8 years	110 mg
9 years and older, including pregnancy and breastfeeding	350 mg

You may notice that the limit sits below the RDA for some groups. Adult men, for example, need 400 to 420 mg a day but should take no more than 350 mg from supplements. ODS explains that this is not a contradiction: the RDA counts all sources, mostly food, while the UL counts only supplements and medicines.

The main reason for the cap is your gut. Large doses of magnesium salts often loosen stools and can cause nausea and stomach cramps. The part your body does not absorb holds water in the bowel, which is what brings on the diarrhea.

The 350 mg figure also shows up in labeling rules. ODS notes that supplements carrying the FDA’s qualified health claim about magnesium and blood pressure must provide at least 84 mg and no more than 350 mg per serving.

Higher doses are sometimes used under medical supervision. ODS describes migraine studies that used up to 600 mg a day, for example. That is a decision for a clinician who knows your health, not a reason to raise a dose you chose yourself.

Food sources

Green leafy vegetables, beans and other legumes, nuts, seeds and whole grains are the richest everyday sources. ODS estimates that the body absorbs roughly 30 to 40 percent of the magnesium in food. Refining grains strips out much of it, so whole grains do more for your intake than white flour or white rice. Water counts too: tap, mineral and bottled waters range from about 1 mg to more than 120 mg per liter.

Food and serving	Magnesium	Percent of Daily Value
Pumpkin seeds, roasted, 1 ounce	156 mg	37%
Chia seeds, 1 ounce	111 mg	26%
Almonds, dry roasted, 1 ounce	80 mg	19%
Spinach, boiled, half a cup	78 mg	19%
Cashews, dry roasted, 1 ounce	74 mg	18%
Peanuts, oil roasted, quarter cup	63 mg	15%
Soymilk, plain or vanilla, 1 cup	61 mg	15%
Black beans, cooked, half a cup	60 mg	14%
Edamame, shelled, cooked, half a cup	50 mg	12%
Peanut butter, smooth, 2 tablespoons	49 mg	12%
Potato, baked with skin, 3.5 ounces	43 mg	10%
Brown rice, cooked, half a cup	42 mg	10%
Yogurt, plain, low fat, 8 ounces	42 mg	10%
Banana, 1 medium	32 mg	8%

These values come from the ODS food table, which draws on USDA FoodData Central. The “percent of Daily Value” column is the figure you see on food and supplement labels. The Daily Value for magnesium is 420 mg for adults and for children aged 4 and older, so a food listed at 10% gives you about 42 mg.

The table shows how quickly ordinary food adds up. A handful of almonds, a bean dish and a serving of leafy greens together cover a large share of most adults’ needs before any supplement comes into it.

What a magnesium-rich day can look like

Using the figures in the table, here is one ordinary day of food that gets close to, or reaches, an adult RDA without a supplement:

• Breakfast: a cup of soymilk with cereal or oats, about 61 mg from the soymilk alone.
• Snack: an ounce of dry roasted almonds, about 80 mg, and a medium banana, about 32 mg.
• Lunch: half a cup of cooked black beans with half a cup of cooked brown rice, about 60 mg and 42 mg.
• Dinner: half a cup of boiled spinach on the side, about 78 mg.

That comes to roughly 353 mg (61 + 80 + 32 + 60 + 42 + 78). It does not yet count bread, yogurt, potatoes, fish or the water you drink. It is enough for most women and close to the target for most men.

The point is not to follow this menu. It is to show that a supplement often fills a smaller gap than people assume. If your meals regularly include foods like these, a lower-dose supplement, or none at all, may be all you need.

Are you getting enough?

Plenty of people fall short on intake. ODS reports that an analysis of national survey data from 2013 to 2016 found 48 percent of Americans of all ages took in less magnesium from food and drinks than the Estimated Average Requirement. Men aged 71 and older and teenagers of both sexes were the most likely to have low intakes.

ODS also lists groups at higher risk of not getting enough:

• people with gut conditions such as Crohn’s disease or celiac disease
• people with type 2 diabetes
• people with alcohol dependence
• older adults, who tend to eat less magnesium, absorb less of it and lose more in their urine

Checking your own status is harder than it sounds. There is no current national data on magnesium status in the United States, and magnesium is not part of the routine electrolyte tests done in hospitals and clinics. What you eat is the usual stand-in, which is why tracking your food for a few days is a reasonable first step.

Signs of low intake

ODS describes the early signs of deficiency as loss of appetite, nausea, vomiting, tiredness and weakness. As it gets worse, people can have numbness, tingling, muscle contractions and cramps, seizures, personality changes, abnormal heart rhythms and spasms of the heart’s arteries. Severe deficiency can also lower blood calcium or potassium.

Low intake is common, but true deficiency is not. MedlinePlus, the U.S. National Library of Medicine’s medical encyclopedia, notes that it is rare to be truly lacking in magnesium. Deficiency with symptoms is uncommon in healthy people and is usually tied to illness, medicines or heavy drinking. The early signs overlap with many other conditions, so they are a reason to see a clinician rather than a reason to start dosing yourself.

Signs of too much

From supplements, the first sign is usually loose stools, sometimes with nausea and cramps. True toxicity is rare. It has mostly been linked to very large doses from laxatives and antacids, typically more than 5,000 mg a day. ODS lists low blood pressure, nausea, vomiting, facial flushing, trouble passing urine, depression and lethargy, which can progress to muscle weakness, difficulty breathing, irregular heartbeat and cardiac arrest. The risk rises sharply when the kidneys are not working well.

Working out your own number

1. Find your RDA in the age table above, or in the lookup tool.
2. Estimate what you already get from food, using the food table or a food-tracking app for a few typical days.
3. If there is a gap, close it with food first. If you still want a supplement, keep the supplement portion at or below 350 mg a day.
4. Pick a form using our glycinate vs citrate comparison or the full table of magnesium types, and plan timing with our guide to when to take magnesium.

Who should be careful

• People with kidney disease: your body cannot clear extra magnesium normally, so take supplements only on medical advice.
• Parents of young children: the supplement limit is 65 mg at ages 1 to 3 and 110 mg at ages 4 to 8, so adult products are not suitable. Ask your pediatrician before giving any.
• People who use magnesium laxatives or antacids: the magnesium in these counts toward the 350 mg limit, so add it up before taking a supplement too.
• People on certain medicines: tetracycline or quinolone antibiotics, oral bisphosphonates (bone-strengthening tablets), diuretics (water pills) and long-term proton pump inhibitors (stomach acid reducers) either interact with magnesium or change how much your body keeps. Ask your pharmacist about timing and dose before you start.
• Anyone with ongoing symptoms: persistent cramps, numbness or a racing or fluttering heartbeat need a clinician’s assessment, not a supplement.