Magnesium intake.

Worked example

A man aged 31 to 50 (RDA 420 mg) gets 300 mg from food and takes a 200 mg supplement. Total: 300 + 200 = 500 mg, or 119% of the RDA. His supplement is 200 ÷ 350 = 57% of the 350 mg supplement upper limit, so he is under it.

How it works

Total = food + supplements, compared with the RDA. RDAs (mg): 80 at ages 1 to 3, 130 at 4 to 8, 240 at 9 to 13; for 14 to 18, 410 (male) and 360 (female); for adults 19 to 30, 400 (male) and 310 (female); for 31 and over, 420 (male) and 320 (female). Pregnancy: 400, 350 and 360 mg for 14 to 18, 19 to 30 and 31 to 50; breastfeeding: 360, 310 and 320 mg.

The upper limit is for supplemental magnesium only, not for magnesium naturally in food: 65 mg at ages 1 to 3, 110 mg at 4 to 8 and 350 mg from age 9, including pregnancy and breastfeeding. Because of that, the tool checks only the supplement amount against the UL.

Sources (opened 2026-10-08): NIH Office of Dietary Supplements, Magnesium: Fact Sheet for Health Professionals.

FAQ

How much magnesium do I need per day?

Adult men need 400 to 420 mg a day and adult women 310 to 320 mg, depending on age. Needs are higher in pregnancy at ages 19 to 30 (350 mg) and 31 to 50 (360 mg).

What is the magnesium upper limit?

The upper limit is 350 mg a day for supplemental magnesium from age 9 up. It does not apply to magnesium found naturally in food. For children it is 65 mg at ages 1 to 3 and 110 mg at ages 4 to 8.

Does the 350 mg limit include food?

No. The NIH table is for supplemental magnesium, so this tool compares only the supplement amount with 350 mg.

Can magnesium supplements affect medication?

They can interact with some medicines. Check with a pharmacist if you take medication, have kidney disease or are pregnant.

Check the other minerals on your label with the potassium and sodium check and the calcium intake calculator.