Magnesium is involved in muscles, nerves, energy and bone. Labels can list either the salt weight or the elemental magnesium, which changes the maths a lot.
Calculator Official intake Study doses Best form Safety Sources
AI (adequate intake)
| Men | 350 mg |
|---|---|
| Women | 300 mg |
| Pregnancy | 300 mg |
| Breastfeeding | 300 mg |
Safe upper limit: 250 mg a day
Safe limit is for magnesium from supplements, water and added to foods only, not magnesium naturally in food.
RDA (recommended dietary allowance)
| Men 18-30 | 400 mg |
|---|---|
| Men 31+ | 420 mg |
| Women 18-30 | 310 mg |
| Women 31+ | 320 mg |
| Pregnancy 18-30 | 350 mg |
| Pregnancy 31+ | 360 mg |
| Breastfeeding 18-30 | 310 mg |
| Breastfeeding 31+ | 320 mg |
Safe upper limit: 350 mg a day
Safe limit is for magnesium from supplements and medicines only, not from food and water.
Source: National Academies (NASEM) 2019
These are doses tested in research, not personal advice. Some exceed the upper limit because they were short courses or given under medical care.
300-368 mg a day
Meta-analysis of 34 trials (2,028 people): a median 368 mg a day for 3 months lowered blood pressure by about 2/1.8 mmHg. 300 mg a day for a month was enough to raise blood magnesium. Effects were mostly in people low in magnesium.
600 mg a day
81 adults with migraine took 600 mg magnesium a day (as trimagnesium dicitrate) or placebo for 12 weeks. Attacks fell by 42% vs 16% with placebo. Diarrhoea affected about 1 in 5. This dose is above both safe limits, so it is usually taken with a doctor's advice.
Best tolerated
Glycinate / bisglycinate, salt weight (~14% Mg)
Why: Glycinate is picked for tolerance, not absorption: loose stools are the main reason people stop taking magnesium. The evidence is thin, one small crossover trial in 12 patients after bowel surgery, where glycinate absorbed about as well as oxide overall and was better tolerated by every patient. On absorption alone, citrate, lactate, aspartate and chloride all beat oxide and sulfate, and no trial puts one of those four ahead of the others.
Alternatives: Citrate is cheap, well absorbed and useful if you are also constipated. Oxide has a lot of magnesium per tablet but is absorbed less and acts mostly as a laxative. High doses of any form can cause diarrhoea.
NIH Office of Dietary Supplements 2026 · Schuette SA et al. 1994
Elemental shares for salts are typical values. Most EU and US labels already list the elemental amount, so pick the first option when unsure.
Nuts, seeds, whole grains, legumes, leafy greens, dark chocolate.
Take 2 or more hours apart from some antibiotics (tetracyclines, quinolones), thyroid hormone and bisphosphonates. Kidney disease: ask a doctor first.
The safe limit is for supplement magnesium only. Going over it mostly causes diarrhoea (oxide and citrate more than glycinate).
Pregnant, breastfeeding, on medication, or managing a health condition? Check with a doctor or pharmacist before starting a supplement.
Values checked: November 12, 2026.
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