Magnesium glycinate, citrate, oxide: how much magnesium is really in it

Magnesium in a supplement is always bound to something else – glycine, citric acid, oxygen. The front of the bottle often shows the weight of the whole compound. The Supplement Facts show how much of it is magnesium – and that can be a seventh of the big number.

How much of the compound is magnesium?

So “magnesium glycinate 1,000 mg” on the front means about 140 mg of magnesium. Oxide has the most magnesium per gram – that’s why oxide tablets can be small. We don’t compare how well the forms are absorbed or how they work – only how much magnesium you get for your money.

What 200 mg of magnesium costs

Of the 627 products we checked, the most expensive costs 488 times as much per 200 mg of magnesium as the cheapest.

Small capsules, small amounts

One capsule or tablet has 11–500 mg of magnesium in the products we checked. For 200 mg you’d need up to 19 of them. Check the serving size: the amount in the Supplement Facts is often for two or three capsules.

Why we compare per 200 mg

The NIH (opens in a new tab) recommends 310–420 mg of magnesium a day for adults, from food and supplements together. For magnesium from supplements, the upper limit for adults is 350 mg a day. 200 mg is a round number in between – it makes products comparable, it’s not a recommendation.

184 of the 627 products we checked have more than 350 mg in one serving. The price list marks them.

All 627 products, sorted by cost per 200 mg of magnesium: magnesium prices.