Quick answer
NIH sets upper limits for magnesium from supplements and medicines that rise with age: 65 mg a day at ages 1 to 3, 110 mg at 4 to 8, and 350 mg from age 9. NIH reports a death in a 28-month-old after very large laxative and antacid doses. Ask your doctor before giving a child a supplement.1
Key facts
- NIH's upper limits for supplemental magnesium are 65 mg a day at ages 1 to 3, 110 mg at 4 to 8 and 350 mg at ages 9 to 18. None is set for babies under 12 months.1
- NIH's recommended amounts from all sources are 80 mg at ages 1 to 3, 130 mg at 4 to 8, 240 mg at 9 to 13, and 410 mg for boys and 360 mg for girls at 14 to 18.1,2
- NIH names teenage girls and boys among the groups most likely to get too little magnesium from food.1
- Fatal magnesium toxicity has been reported in a 28-month-old boy after very large doses from laxatives and antacids, typically above 5,000 mg a day.1
- A magnesium citrate laxative label lists doses by age band and says to ask a doctor for children under 2.3
Magnesium limits and recommended amounts by age
| Age | Recommended amount from all sources | Upper limit from supplements and medicines |
|---|---|---|
| 0 to 6 months | 30 mg (adequate intake) | None established |
| 7 to 12 months | 75 mg (adequate intake) | None established |
| 1 to 3 years | 80 mg | 65 mg |
| 4 to 8 years | 130 mg | 110 mg |
| 9 to 13 years | 240 mg | 350 mg |
| 14 to 18 years | 410 mg for boys, 360 mg for girls | 350 mg |
For several ages the upper limit sits below the recommended amount. NIH explains why: the recommended amounts include magnesium from every source, while the limits count only supplements and medicines, not the magnesium that occurs naturally in food and drinks.1
Magnesium that is naturally present in food and drinks is not harmful and does not need to be limited; the upper limit applies to supplements and medicines only.2
What too much magnesium can do in a child
High intakes of magnesium from supplements and medicines can cause diarrhea, nausea and abdominal cramping.2
NIH's health professional sheet reports that very large doses of magnesium-containing laxatives and antacids, typically above 5,000 mg of magnesium a day, have caused toxicity, including a fatal case in a 28-month-old boy. These were very large doses, far above the upper limits in the table.1
The risk of magnesium toxicity rises when the kidneys work poorly or have failed, because they cannot remove the excess.1
Where children meet magnesium besides supplements
Magnesium also comes in multivitamin and mineral products and in laxatives and antacids. The Drug Facts label on a magnesium citrate laxative divides directions into age bands from 2 up to 12 and over, and tells caregivers to ask a doctor for children under 2. Both it and a magnesium oxide antacid label say to keep the product out of reach of children.2,3,4
Because these products add magnesium on top of food, a child's total from supplements and medicines is what NIH's upper limit measures. Ask your pharmacist to add up everything a child takes.1
Do teens get enough magnesium from food?
In national survey data from 2013 to 2016, 48% of Americans of all ages took in less magnesium from food and drinks than the amount NIH uses as a typical requirement, and adolescent boys and girls were among those most likely to fall short. NIH adds that people should get most nutrients from food, and that supplements can be useful when needs are hard to meet that way.1,2
NIH says to be careful about giving supplements to a child unless a health care provider recommends them, because many supplements have not been well tested for safety in children.5
Who should ask their doctor
- A parent considering a magnesium supplement for a child of any age. Ask your doctor first, as NIH advises for any supplement given to a child.5
- A teen or child with kidney disease or a medical condition, because the kidneys remove excess magnesium and NIH says toxicity risk rises when they cannot.1
- A child or teen taking antibiotics, an oral bisphosphonate, a diuretic or an acid reflux medicine, which NIH names as medicines magnesium can interact with or affect.1
Questions people ask
Is magnesium safe for teens to take?
NIH sets the same 350 mg a day upper limit from supplements and medicines for ages 9 to 18. Ask your doctor before a teen uses a supplement, especially with a medical condition or medicines.1
Is magnesium good for teens?
NIH names teens among the groups most likely to get too little magnesium from food, and says people should get most nutrients from food. Whether a supplement fits a particular teen is a question for a doctor.1,2
Is magnesium good for teens with ADHD?
The sources on this page do not address ADHD. That is not a finding either way, so ask your doctor before giving a teen with a medical condition a supplement.1
Is magnesium safe for teen boys?
NIH gives boys and girls aged 14 to 18 the same 350 mg a day upper limit for supplements, and a higher recommended amount for boys (410 mg) than for girls (360 mg).1
Is magnesium ok for teens who play sports?
The NIH magnesium sheets do not give separate limits for athletes. The upper limit for ages 9 to 18 is 350 mg a day from supplements and medicines, and a doctor can look at the whole picture.1
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Sources
- National Institutes of Health, Office of Dietary Supplements. Magnesium: Fact Sheet for Health Professionals. Updated January 6, 2026. Opened 2026-10-06.
- Office of Dietary Supplements, National Institutes of Health. Magnesium: Fact Sheet for Consumers. Updated March 22, 2021. Opened 2026-10-06.
- Walgreens Magnesium Citrate Oral Solution, saline laxative: Drug Facts label (Walgreen Co.). DailyMed, U.S. National Library of Medicine. Label effective July 20, 2026. Opened 2026-10-07.
- Magnesium Oxide 400 mg tablets, antacid: Drug Facts label (Westminster Pharmaceuticals). DailyMed, U.S. National Library of Medicine. Label effective July 6, 2026. Opened 2026-10-07.
- National Institutes of Health, Office of Dietary Supplements. Dietary Supplements: What You Need To Know. Fact sheet for consumers. Updated January 4, 2023. Opened 2026-10-07.
This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.