The Two Numbers on a Magnesium Label, and Which One Is Real

Pick up almost any magnesium bottle and you will find more than one number on it. One sits on the front or in the product name. Another sits in the Supplement Facts panel. They rarely match, and the gap can be large. This post does the arithmetic once, so you can check any label yourself in about a minute.

1. Restore's 500 mg and 90 mg explained

For Lunia Restore, 500 mg describes the magnesium bisglycinate ingredient amount, while 90 mg describes the elemental magnesium provided by a two-capsule serving. The 90 mg figure is the amount to compare with magnesium intake references. It is not 500 mg of elemental magnesium.

The theoretical magnesium fraction of pure, anhydrous magnesium bisglycinate is about 14.1 percent, calculated from its molecular formula. That calculation describes a specific chemical form, not every commercial ingredient sold under the glycinate name. Commercial grades can differ, including buffered materials. Read the product-specific Supplement Facts panel and supplier specification rather than treating one theoretical percentage as a universal conversion. This distinction does not identify the composition of Restore's raw material.

2. Why a label can show both numbers

The Supplement Facts panel is regulated. FDA's labeling rule for dietary supplements says the amount listed for a nutrient has to represent the weight of the dietary ingredient itself, with calcium versus calcium carbonate as the rule's own example. For magnesium, that means the panel reports magnesium, not magnesium glycinate.

Citation: U.S. Food and Drug Administration. 21 CFR 101.36, Nutrition labeling of dietary supplements. Electronic Code of Federal Regulations. eCFR: 21 CFR 101.36

Product names, front-of-bottle claims and ad copy are a different surface. They can mention the compound weight, and plenty of them do. Neither number is automatically wrong. The skill is knowing which one answers your question, and for "how much magnesium am I swallowing," it is the panel.

3. The percent Daily Value check (20 seconds)

The panel usually prints a percent Daily Value next to the milligrams. FDA sets the magnesium Daily Value at 420 mg. That gives you a built-in cross-check. Divide the milligrams by the percent, then multiply by 100. If the answer lands near 420, the milligram figure is elemental magnesium.

Citation: U.S. Food and Drug Administration. Daily Value on the Nutrition and Supplement Facts Labels. FDA.gov. FDA: Daily Value table

Two illustrative panels. A line reading 210 mg at 50 percent gives 210 divided by 50, times 100, which is 420. A line reading 400 mg at 95 percent gives 421. Both check out. Percentages are rounded, so expect a point or two of drift. Labels printed before the Daily Value changed may land near 400 instead, which dates the artwork but says nothing about honesty.

For Restore, use 90 mg of elemental magnesium in this calculation: 90 divided by 420 is about 21 percent of the Daily Value. Using the 500 mg ingredient weight instead would incorrectly calculate about 119 percent. Always check that the milligrams and percent Daily Value refer to elemental magnesium and the same serving size.

4. The capsule count check (10 seconds)

Check the serving size before comparing milligrams. Restore's 90 mg elemental magnesium amount is for two capsules, not one. A different product may list its amounts for one, two or more capsules.

Capsule size alone cannot verify a dose: powder density, excipients and the magnesium ingredient's specification all affect fill weight. If the ingredient weight and elemental amount are unclear, ask the manufacturer how the serving was formulated rather than estimating from capsule count.

5. What the glycine is doing there

In pure magnesium bisglycinate, much of the compound's mass comes from the glycinate portion. That does not make it filler. Glycine is the reason the form exists. Magnesium needs a carrier, and the carrier decides what the compound is like to take. The comparison most people have in mind is magnesium oxide, which is 60.3 percent magnesium by weight and therefore a very dense source. A human crossover study that measured urinary magnesium found fractional absorption of oxide around 4 percent.

Citation: Firoz M, Graber M. Bioavailability of US commercial magnesium preparations. Magnes Res, 2001. PubMed: 11794633

That 4 percent figure belongs to oxide and to that study's method. It does not translate into a matching percentage for glycinate, and you should be wary of any page that sets "oxide 4 percent" against a clean number for the chelated form. A 60-day randomized trial of 46 healthy adults, dosed at 300 mg of elemental magnesium a day, found that an amino acid chelate and citrate both showed greater absorption than oxide by 24-hour urinary excretion, and that citrate gave the highest serum levels. That chelate was an amino acid chelate, not specifically bisglycinate, so it supports the general idea and stops short of ranking glycinate.

Citation: Walker AF, Marakis G, Christie S, Byng M. Mg citrate found more bioavailable than other Mg preparations in a randomised, double-blind study. Magnes Res, 2003. PubMed: 14596323

6. Why glycinate is the usual pick for sleep

Three reasons, in order of how much evidence sits behind them.

First, and most concrete: bisglycinate is the form with a dedicated sleep trial. In a randomized, double-blind, placebo-controlled study of 155 adults reporting poor sleep, 250 mg of elemental magnesium as bisglycinate lowered Insomnia Severity Index scores by 3.9 points over four weeks, against 2.3 points on placebo (p = 0.049). The authors called the effect small (Cohen's d of 0.2) and noted the benefit looked larger in people whose diets were lower in magnesium. The trial did not use objective sleep measures, and four weeks is a short window.

Citation: Schuster J, Cycelskij I, Lopresti A, Hahn A. Magnesium Bisglycinate Supplementation in Healthy Adults Reporting Poor Sleep: A Randomized, Placebo-Controlled Trial. Nat Sci Sleep, 2025. PubMed: 40918053

Second, glycinate is generally described as gentler on the gut than oxide or citrate, which matters for something taken nightly. That description rests more on convention and mechanism than on head-to-head trials, so treat it as a reasonable expectation, not a measured result.

Third, and this is the caveat: no trial we are aware of puts glycinate against other forms for sleep. The sleep evidence for any single form is thin, which is part of why we compare forms in our magnesium forms guide without crowning a winner. Glycinate has the one dedicated sleep trial and a reputation for being easy on the stomach. That is a good reason to choose it, and a narrower claim than naming a winner.

7. How much magnesium you actually need

The Daily Value is 420 mg for adults, and it counts everything: food plus supplements. The Tolerable Upper Intake Level for magnesium from supplements alone is 350 mg for adults. It sits below the Daily Value because it applies only to the supplemental portion, which is where the risk of loose stools and cramping comes from. Past a certain dose, high amounts from supplements can cause diarrhea, nausea and abdominal cramping, and very high doses carry more serious risks.

Citation: National Institutes of Health, Office of Dietary Supplements. Magnesium: Health Professional Fact Sheet. NIH ODS. NIH ODS fact sheet

More is not better here. Because the kidneys clear excess magnesium, anyone with kidney problems, or anyone taking medications that interact with magnesium, should talk to a clinician before adding a supplement. For dose context across the usual sleep ingredients, see our sleep stack dosing norms.

Where Lunia fits

Lunia Restore lists 90 mg of elemental magnesium per two-capsule serving on the Supplement Facts panel, provided by 500 mg of magnesium bisglycinate. That is the kind of number this post has been teaching you to look for. It sits below the 250 mg elemental dose used in the Schuster trial, and we say so. Restore is built around magnesium working alongside L-theanine and apigenin, not as a standalone magnesium dose. There is no randomized trial on the finished formula. Individual results may vary.

Learn more about Lunia Restore

Frequently Asked Questions

What does "elemental magnesium" mean on a supplement label?

It means the weight of the magnesium itself, not the weight of the whole ingredient it comes in. Magnesium is always attached to something, such as glycine or citrate, and the compound weighs more than the magnesium alone. US rules say the Supplement Facts panel has to report the magnesium, so that is the number to read.

How much elemental magnesium is in 500 mg of magnesium glycinate?

In Lunia Restore, 500 mg of magnesium bisglycinate provides 90 mg of elemental magnesium per two-capsule serving. Do not assume the same conversion for every product. Pure anhydrous bisglycinate has a theoretical magnesium fraction of about 14.1 percent, while commercial ingredient specifications can differ. Check the elemental amount and serving size on the product label.

Why does my label show two different magnesium numbers?

One is usually the compound weight, often in the product name or on the front, and the other is the elemental weight on the Supplement Facts panel. They describe the same capsule in two different ways. The panel number is the one the rules apply to.

Is 100 mg of elemental magnesium a low dose?

It is about 24 percent of the 420 mg Daily Value and well under the 350 mg supplemental upper limit. Whether it is low depends on your diet and on what you are comparing it with. The one bisglycinate sleep trial in our references used 250 mg elemental, so 100 mg is below that dose.

How many capsules should a real magnesium glycinate serving be?

There is no universal capsule count. Lunia Restore uses a two-capsule serving that provides 90 mg of elemental magnesium. For other products, check the serving size and elemental magnesium amount on the Supplement Facts panel; capsule size alone does not verify the dose.

What is the difference between the 420 mg Daily Value and the 350 mg upper limit?

The Daily Value is a labeling reference for total intake from food and supplements. The 350 mg upper limit applies to magnesium from supplements and medications only. They measure different things, which is why the limit can sit below the Daily Value.

Is the glycine in magnesium glycinate just filler?

No. Glycine is the amino acid that the magnesium is bound to, and it is the reason the compound weighs so much more than the magnesium it carries. Whether the bound form changes how you feel is a separate question, and the evidence on that is thinner than the marketing suggests.

The Bottom Line

Read the elemental magnesium amount and the serving size together. For Restore, that means 90 mg of elemental magnesium from 500 mg of magnesium bisglycinate per two-capsule serving. Use the Supplement Facts panel, not a universal conversion or capsule-size estimate, to compare products. The 420 mg Daily Value is a labeling reference, and the 350 mg adult upper limit applies to magnesium from supplements and medications. Check with a clinician if you have kidney concerns.

References

1. U.S. Food and Drug Administration. 21 CFR 101.36, Nutrition labeling of dietary supplements. Electronic Code of Federal Regulations. eCFR: 21 CFR 101.36
2. U.S. Food and Drug Administration. Daily Value on the Nutrition and Supplement Facts Labels. FDA.gov. FDA: Daily Value table
3. Firoz M, Graber M. Bioavailability of US commercial magnesium preparations. Magnes Res. 2001;14(4):257-262. PubMed: 11794633
4. Walker AF, Marakis G, Christie S, Byng M. Mg citrate found more bioavailable than other Mg preparations in a randomised, double-blind study. Magnes Res. 2003;16(3):183-191. PubMed: 14596323
5. Schuster J, Cycelskij I, Lopresti A, Hahn A. Magnesium Bisglycinate Supplementation in Healthy Adults Reporting Poor Sleep: A Randomized, Placebo-Controlled Trial. Nat Sci Sleep. 2025;17:2027-2040. PubMed: 40918053
6. National Institutes of Health, Office of Dietary Supplements. Magnesium: Health Professional Fact Sheet. NIH ODS. NIH ODS fact sheet

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.