Quick answer

Count the magnesium, not the compound. Adults need 310 to 420 mg of magnesium a day from food and supplements together, and magnesium from supplements and medicines should stay at or under 350 mg a day unless a doctor advises more. The limit is the same whether the label says citrate, glycinate or oxide.^1,2

Key facts

A 400 mg magnesium oxide tablet supplies 241.3 mg of magnesium, while an 893 mg capsule of magnesium bisglycinate supplies 125 mg.^3,4
The Daily Value printed on labels is 420 mg, the top of the adult range.²
In the European Union the limit for supplemental magnesium is lower than in the US: 250 mg a day.⁵
One adult dose of a liquid magnesium citrate laxative holds about 1,900 to 2,900 mg of magnesium.⁶

Recommended amounts by age

Magnesium needed per day, from all sources²
Who	Amount per day
Children 1 to 3	80 mg
Children 4 to 8	130 mg
Children 9 to 13	240 mg
Teens 14 to 18	410 mg for boys, 360 mg for girls
Men 19 to 30	400 mg
Men 31 and older	420 mg
Women 19 to 30	310 mg
Women 31 and older	320 mg
Pregnancy	400 mg for teens, 350 to 360 mg for adults
Breastfeeding	360 mg for teens, 310 to 320 mg for adults

These amounts count everything you swallow: food, drinks, supplements and medicines. NIH sets them by age, sex and life stage. It gives no amount per kilogram of body weight and no extra allowance for exercise.²

Counting citrate, glycinate and oxide

The Supplement Facts panel lists the amount of magnesium itself, not the weight of the whole compound, so that is the figure to compare between forms.²

Compound weight against the magnesium it supplies^2,3,4,6,7
Product	Compound	Magnesium
Magnesium oxide antacid tablet	400 mg	241.3 mg
Magnesium bisglycinate capsule from the sleep trial	893 mg	125 mg
Magnesium L-threonate, as used in trials	1 g	about 75 mg
Liquid magnesium citrate laxative	1,745 mg per fluid ounce	290 mg per fluid ounce
Milk of Magnesia, as magnesium hydroxide	1 tablespoon	500 mg

So the 350 mg limit is passed by two of those oxide tablets, or by three of those bisglycinate capsules. Citrate tablets and powders work the same way: the magnesium line on the label is the number that counts, whatever the compound weighs.^1,3,4

Amounts used in studies

Trials of magnesium supplements in adults have used 197 to 994 mg of magnesium a day. Pooling 48 of them, blood magnesium rose with the daily amount until about 300 mg a day and then leveled off.⁸

The higher a person's blood magnesium at the start, the less it rose with supplements, and the more was passed in urine. A bigger dose does not keep filling the body.⁸

The single trial of bisglycinate for sleep used 250 mg of magnesium a day, under the limit. The two L-threonate trials used 1 to 2 g of that compound a day, which is only about 75 to 145 mg of magnesium.^4,7,9

The upper limit, and when it is passed

The upper limit for magnesium from supplements and medicines is 350 mg a day for adults. It does not count magnesium in food and drinks.^1,2

For children, the upper limit for magnesium from supplements and medicines is 65 mg a day at ages 1 to 3, 110 mg at 4 to 8, and 350 mg from age 9. No limit is set for infants.^1,2

In the European Union, the upper level for magnesium from supplements, water and fortified foods is 250 mg a day for adults, including during pregnancy and breastfeeding. Like the US limit, it leaves out magnesium naturally present in food.⁵

Laxatives and antacids can pass the limit in a single dose. One adult dose of liquid magnesium citrate is 6.5 to 10 fluid ounces, about 1,900 to 2,900 mg of magnesium. NIH notes that part of a laxative dose is not absorbed, because the laxative effect carries it through, and the label is for occasional use only.^2,6

Some studies in people with migraine used up to 600 mg a day. NIH says amounts above the upper limit should be taken only under a doctor's direction.²

People with kidney disease or reduced kidney function should not take magnesium supplements without medical advice, because their kidneys may not clear the excess.²

What's in ours

What’s in ours

Magnesium Glycinate: Magnesium, 275 mg per serving, from the label
Men's Multi: Magnesium, 50 mg per serving, from the label
Creatine + Electrolytes: Magnesium, 60 mg per serving, from the label

If you take more than one of these, add the magnesium lines together and compare the total with the 350 mg limit.¹

Questions people ask

How much magnesium glycinate should I take per day?

Go by the magnesium line, not the weight of the glycinate. The one sleep trial of this form used 250 mg of magnesium a day, and adults should stay at or under 350 mg a day from supplements unless a doctor advises more.^1,4

How much magnesium oxide per day?

A 400 mg oxide tablet supplies 241.3 mg of magnesium, so one tablet is within the 350 mg adult limit and two are above it. The antacid label allows up to two tablets in 24 hours, so check with a doctor before taking two a day for long.^1,3

Is 500 mg of magnesium a day too much?

From supplements and medicines, yes: 500 mg is above the 350 mg adult limit, so take it only on a doctor's advice. Magnesium in food does not count toward that limit.¹

Do active people need more magnesium?

NIH gives no extra amount for exercise. In a pooled analysis of 14 trials, magnesium supplements did not raise strength or power in people who were not short of it.^2,10

See what we make

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See the Full Measure line Creatine + Electrolytes Magnesium Glycinate Men's Multi

Sources

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.