Is Magnesium Safe for Kids? Side Effects and Upper Limits

The short answer: yes, magnesium is safe for healthy children at the doses used in children's supplements. Magnesium from food is never a problem for healthy kidneys. With supplements, the most common side effect is loose stools at higher doses or with harsher forms. Stay within the dose for your child's age, and check with your GP first if your child has kidney problems, a medical condition or takes medication.

Food vs supplements

Healthy kidneys simply remove any extra magnesium that comes from food, so there is no upper limit for magnesium in a normal diet. Upper limits apply only to magnesium from supplements and fortified foods, because large amounts taken at once can upset the gut.

Official upper limits

• Europe (EFSA): 250mg a day of supplemental magnesium for children aged 4 and over and for adults. No level has been set for children aged 1 to 3.
• United States: lower limits for young children, at 65mg a day of supplemental magnesium for ages 1 to 3, 110mg for ages 4 to 8 and 350mg from age 9.

Children's supplements are dosed with these in mind. Ours gives 35mg for ages 1 to 5 and 70mg for ages 5 to 14, within both sets of limits.

Possible side effects

• Loose stools or diarrhoea, the classic sign of too much magnesium or a poorly absorbed form such as oxide.
• Tummy cramps or nausea, more likely if the dose is taken on an empty stomach or all at once.

Gentle, well-absorbed forms like magnesium glycinate rarely cause these at children's doses. If they do, stop and speak to your pharmacist or GP.

Who should check with a GP first

• Children with kidney problems, because their bodies cannot clear extra magnesium properly.
• Children taking medication. Magnesium can reduce the absorption of some antibiotics and other medicines, so they may need to be taken a few hours apart.
• Children with heart conditions or any long-term condition.
• Babies under 12 months, who should not be given magnesium supplements unless a doctor advises it. See can babies have magnesium?

What too much looks like

Serious magnesium overload is very rare and usually involves kidney failure or very large amounts of magnesium-containing laxatives or antacids. Signs include weakness, unusual sleepiness, nausea and low blood pressure. If you think your child has taken a large amount of any supplement, contact NHS 111 or your GP straight away.

Keeping it safe at home

1. Follow the dose for your child's age on the label, and use the measure provided.
2. Count all sources: if your child takes a multivitamin with magnesium, check the total before adding another product.
3. Store supplements out of reach and sight, especially anything that looks like sweets.
4. Choose a brand that is independently tested, so you know the dose is what the label says. The 2025 MHRA warning about one brand of gummies shows why. Read what happened.

The bottom line

Magnesium is one of the safest supplements for children when it is the right form at the right dose. Food comes first, a top-up fills the gaps. Our magnesium for kids is designed for daily use from age 1: 2.5ml for ages 1 to 5 and 5ml for ages 5 to 14. See how much magnesium kids need by age for the full picture.

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Our magnesium
Liposomal Magnesium for Kids (Age 1+) is truly unflavoured, gentle on little tummies, and built for absorption. Magnesium contributes to the normal functioning of the nervous system.*

*Food supplements should not be used as a substitute for a varied and balanced diet and a healthy lifestyle. Consult your healthcare provider before use if your child has a medical condition or takes medication.