How to Read a Magnesium Label: Elemental Magnesium Explained

Elemental magnesium is the weight of the magnesium itself in a supplement, not counting the compound it's attached to. It's the number that tells you your dose, and on a US label it's the amount listed next to "Magnesium" on the Supplement Facts panel. The big number on the front of the bottle is often something else entirely.

Here's how to read a magnesium label in about thirty seconds, what to check, and the tricks that make products look stronger than they are.

Why "elemental" matters

Magnesium can't be put in a capsule on its own. It's always bound to something: glycine in glycinate, citric acid in citrate, oxygen in oxide. That partner adds weight, and in most forms it's most of the weight.

So two bottles that both say "500 mg" on the front can contain wildly different amounts of magnesium. The elemental number cuts through that.

Reading the Supplement Facts panel

Supplement Facts

Serving Size 2 Capsules
Servings Per Container 60

Amount Per Serving% Daily Value

Magnesium (as magnesium bisglycinate)200 mg 48%

Other ingredients: hypromellose (capsule), microcrystalline cellulose.

Work down the panel in this order.

1. Serving size

Everything else on the panel refers to one serving, and a serving is often two, three or four capsules. A label showing 200 mg per serving with a four-capsule serving gives you 50 mg per capsule. Check this first, because it changes every other number.

2. The magnesium line

Find the row that starts with "Magnesium". The amount on that row is elemental magnesium per serving. The words in brackets tell you the form:

• "Magnesium (as magnesium bisglycinate) 200 mg" means 200 mg of magnesium, all from glycinate.
• "Magnesium (as magnesium bisglycinate, magnesium oxide) 200 mg" means a mix. You can't tell how much comes from each, and the oxide part is the part more likely to upset your stomach.
• "Magnesium (as magnesium citrate, glycinate, malate, taurate) 300 mg" is a blend of forms, sometimes sold as a "complex". It's not necessarily bad, but you won't know the split.

3. % Daily Value

The %DV compares the amount with the FDA's labeling reference of 420 mg. A product with 210 mg shows 50%. It's useful for comparing products quickly, but it isn't a target you have to hit: your food supplies magnesium too.

4. Other ingredients

Below the panel. This is where a second form can hide. If you see magnesium oxide here, or a "buffered" claim on the front, the product isn't pure glycinate. You'll also see the capsule shell and any fillers or flow agents, which are normal in small amounts.

5. Testing seals

A USP Verified or NSF mark means an independent lab has checked that what's on the label is in the bottle. "Made in a GMP facility" is a statement about the factory, not a test of the product. More in our label glossary.

Front-of-bottle tricks

These are the patterns to watch for. None of them are against the rules; they just make products look stronger than they are.

If a product only shows the compound weight and you can't find the elemental figure, our label checker converts it for you.

Calculator Magnesium label checker Turn the big number on the bottle into the real amount of magnesium, for eight common forms. Check your label →

Comparing price fairly

Price per bottle tells you almost nothing, because bottles hold different numbers of servings with different amounts of magnesium. Compare price per 200 mg of elemental magnesium instead:

1. Find the elemental magnesium per serving on the panel.
2. Multiply by the number of servings in the bottle to get total magnesium.
3. Divide the price by that total, then multiply by 200.

For example, a $20 bottle with 60 servings of 200 mg holds 12,000 mg of magnesium. That's about 33 cents per 200 mg. A $15 bottle with 90 servings of 100 mg holds 9,000 mg, which works out at about 33 cents too, even though one looks cheaper on the shelf.

That's the comparison we use in our buying guides.

How much should the label say?

Most people take 200 to 350 mg of elemental magnesium a day, and the NIH sets the upper limit for supplements at 350 mg (NIH ODS). So look for a product where a full serving lands in that range, or one with smaller capsules you can adjust. Our magnesium glycinate dosage guide goes through the numbers.

Questions people ask

What is elemental magnesium?

The weight of the magnesium itself in a supplement, not counting the compound it's bound to. It's the number on the Supplement Facts panel and the one to dose by.

How much elemental magnesium is in magnesium glycinate?

About 14% by weight. So 1,000 mg of magnesium glycinate contains about 140 mg of elemental magnesium.

Is the number on the Supplement Facts panel elemental?

Yes. On US labels, the amount next to Magnesium on the panel is elemental magnesium. The front of the bottle may show the compound weight instead.

TD

Written by Tom D

Tom has trained in the gym for years and has taken 5 g of creatine every day for about a decade, with magnesium on and off for most of the year. Reading the research behind supplements started as a hobby; this site is where he writes it up. He isn't a doctor or dietitian, so every claim links to the study behind it.

Sources

1. NIH Office of Dietary Supplements, Magnesium fact sheet for health professionals
2. Firoz & Graber 2001, Bioavailability of US commercial magnesium preparations

We link to the original study wherever we can. Read how we grade evidence and choose products.