How To Read a Magnesium Label

Everything below can be checked against the bottle in your cupboard. That is the point of it.

1. The number on the front is not the dose

Pick up almost any magnesium supplement and the front will carry a big number. 500 mg. 1,000 mg. Sometimes more.

That number is usually the weight of the compound — magnesium bonded to something else. It is not the weight of the magnesium.

Magnesium is a metal. It does not sit on a shelf as a loose mineral; it has to be bound to a carrier molecule to be stable and swallowable. Glycine, citric acid, oxygen, chloride. The carrier is most of the weight. The magnesium inside it — the part your body is actually after — is called elemental magnesium, and in some forms it is less than a tenth of what the front of the bottle advertises.

So "1,000 mg Magnesium Glycinate" is not a 1,000 mg dose of magnesium. It is roughly 140 mg of magnesium and 860 mg of glycine.

2. Turn it over. The panel has to tell you the truth.

Here is the part most people don't know, and it is the single most useful thing in this article.

The front of a bottle is marketing. It is a product name, and a product name can say almost anything. The Supplement Facts panel on the back is regulated. FDA rules require that minerals be declared by the weight of the element, not the weight of the source ingredient — the agency's own labeling guide puts it plainly: you must list the weight of the mineral "rather than the weight of the … source ingredient."¹

Which means:

• Front of the bottle: can quote the compound. Often does, because the number is bigger.
• Supplement Facts panel: must quote elemental magnesium. The line reading Magnesium — 275 mg is 275 mg of magnesium.

The two numbers can differ by a factor of ten on the same bottle, and both are legal. Nobody is breaking a rule. They are just counting different things, and only one of those things is the thing you came for.

So: ignore the front. Turn it over. Find the word Magnesium in the panel and read the milligrams beside it. That is your dose.

3. What the conversion actually looks like

Every compound has a fixed ratio, set by chemistry rather than by the brand. Here is roughly what 1,000 mg of each common form contains:

Two honest caveats. These are calculated from molecular weight, and real ingredients carry water and sometimes a buffering agent, so a given batch can land a point or two below the theoretical figure — glycinate especially, which is why it is a range here rather than a single number. And a high percentage is not automatically a good thing. Oxide wins this table by a mile and still loses the next one.

4. A big number that doesn't get in is not a dose either

Elemental magnesium tells you what is in the capsule. It does not tell you what crosses into you.

The NIH's own summary is blunt about this: forms that dissolve well are absorbed more completely, and magnesium "in the aspartate, citrate, lactate, and chloride forms is absorbed more completely and is more bioavailable than magnesium oxide and magnesium sulfate."² When commercial preparations were compared head to head, oxide came out at the bottom.³

Oxide's problem is the same property twice over. It is poorly soluble, so a large share of it never leaves the intestine — and magnesium sitting in the intestine pulls water in behind it. That is why oxide is one of the forms most commonly reported to cause diarrhea.² It is also why magnesium oxide is sold on its own as a laxative. Not a side effect. The mechanism.

So oxide is the cheapest form to manufacture, carries the most magnesium per milligram, produces the most impressive number on a label, and is the least likely to reach you. All four of those facts are the same fact.

5. How much you are aiming for

The RDA for adults runs 310–420 mg a day of elemental magnesium depending on age and sex — 400–420 mg for men, 310–320 mg for women.² That is your total from everything: food, water, supplements.

Most people are short. An analysis of NHANES data from 2013–2016 found 48% of Americans take in less magnesium from food and drink than their estimated average requirement.²

There is also a ceiling worth knowing, and it is lower than people expect. The Tolerable Upper Intake Level for magnesium from supplements is 350 mg a day for adults.² It does not apply to magnesium from food. If a supplement puts you near or over that line, the usual result is loose stools rather than anything dangerous — but a bottle promising 500 mg of elemental magnesium in a serving is not being generous with you.

6. The whole check, in four steps

1. Turn the bottle over and find the Supplement Facts panel. Whatever is on the front, stop reading it.
2. Find the line that says "Magnesium" and read the milligrams. That is elemental, by law. That is your real dose.
3. Find the form. It is usually in brackets on the same line, or in Other Ingredients. If the only form named is oxide, the number in step 2 is flattering.
4. Check the serving size at the top of the panel. Panel figures are per serving, and a serving is often two or three capsules. A bottle of 60 capsules at 3 per serving is a 20-day bottle, not a two-month one.

Four steps, maybe thirty seconds. It will tell you more than any front label ever will.

7. And ours

It would be strange to write all of that and not show you our own.

LUVO CALM's panel reads Magnesium 275 mg (from 2,500 mg Magnesium Glycinate), serving size three capsules, 30 servings per container. Both numbers, the form, and the serving size, printed where the rules require them to be true.

275 mg is deliberately under the 350 mg supplemental ceiling. Three capsules rather than one, because 275 mg of elemental magnesium does not fit in one capsule — we could have filled one and called it a daily, and it would have cost us less and done less.

You do not have to take our word for any of it. That is the entire idea.

Sources

1. U.S. Food & Drug Administration. Dietary Supplement Labeling Guide: Chapter IV, Nutrition Labeling.
2. NIH Office of Dietary Supplements. Magnesium: Fact Sheet for Health Professionals.
3. Firoz M, Graber M. Bioavailability of US commercial magnesium preparations. Magnesium Research. 2001;14(4):257–62.

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.