Most adults need between 310mg and 420mg of elemental magnesium a day, depending on age and sex. Most supplements do not tell you how much elemental magnesium they contain, which is why the question is harder to answer than it should be.
The number on the bottle is usually not the answer
A bottle reading "Magnesium Glycinate 2,500mg" is telling you the weight of the whole compound: the magnesium plus the glycine it is bound to. The actual mineral is a fraction of that. In that example it is roughly 275mg.
So when you ask "how much magnesium do I need," the recommended intakes below refer to elemental magnesium, and you have to find that figure on the label before you can compare anything.
Recommended daily intakes
These are the US Recommended Dietary Allowances for magnesium, total intake from food and supplements combined.
| Group | RDA (elemental) |
|---|---|
| Men 19–30 | 400 mg |
| Men 31+ | 420 mg |
| Women 19–30 | 310 mg |
| Women 31+ | 320 mg |
| Pregnancy | 350–360 mg |
You are probably getting some from food
This matters, because supplement doses are meant to fill a gap, not to replace the whole RDA. Rough magnesium content of common foods:
- Pumpkin seeds, 1 oz — about 150 mg
- Chia seeds, 1 oz — about 111 mg
- Almonds, 1 oz — about 80 mg
- Spinach, cooked, half cup — about 78 mg
- Black beans, half cup — about 60 mg
- Dark chocolate 70%, 1 oz — about 65 mg
- Avocado, one medium — about 58 mg
National survey data consistently shows a large share of US adults fall short of the RDA from diet alone, but "short" usually means falling 100–150mg below it, not starting from zero.
So what should a supplement provide?
If your diet is providing 200–250mg and the RDA is 310–420mg, a supplement in the range of 200–350mg elemental closes the gap without overshooting. This is why most well-formulated magnesium supplements sit in that band, and why a product advertising "1,000mg magnesium" is either counting compound weight or giving you far more than you need.
The upper limit is not what most people assume
The Tolerable Upper Intake Level for supplemental magnesium is 350mg a day for adults. That limit applies only to magnesium from supplements, not from food — magnesium from food has no upper limit, because the body regulates absorption from food effectively.
Exceeding the supplemental limit does not usually cause anything dramatic. The first sign is loose stools, because unabsorbed magnesium draws water into the intestine. That is also why magnesium citrate at high doses is used as a laxative, and why the form you choose changes how much you tolerate.
How to work out your own number
- Find the RDA for your age and sex in the table above.
- Estimate your food intake honestly. If you eat nuts, seeds, leafy greens or beans most days, assume 250–300mg. If you rarely eat those, assume 150–200mg.
- Subtract. The difference is roughly what a supplement should provide.
- Check the elemental figure on the label — not the compound weight — and pick something close to that number.
What we do
Our magnesium is glycinate at 275mg elemental per three-capsule serving, from 2,500mg of the compound. Both figures are printed on the front. 275mg sits deliberately below the 350mg supplemental upper limit, which leaves room for what you are already eating.
An honest limitation: 275mg is a general-purpose amount. If a blood test has shown you are genuinely deficient, your doctor may want you on more than that, and you should follow them rather than us.
Before you start
Magnesium can interfere with the absorption of certain antibiotics (tetracyclines and quinolones) and bisphosphonates — space those at least two hours apart. If you have reduced kidney function, speak to your doctor before taking any magnesium supplement, because impaired kidneys clear it less effectively.
*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.
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