Method
Solving a proprietary blend, not just bounding it
A proprietary blend is designed to be unreadable. It declares one total and withholds every individual amount, and that is lawful. Most of the time a reader gets ceilings and has to live with them. Occasionally a label hands over a second figure without meaning to, and then the blend can be solved rather than merely bounded. This is the best worked example this desk has had.
The whole method in four numbers. The panel declares 80 mg of elemental magnesium at 19% of the Daily Value, sourced from the magnesium glycinate from proprietary blend. Magnesium bisglycinate is 14.1% magnesium by weight — 24.305 of a molar mass of 172.42 — so 80 ÷ 0.141 gives about 567.5 mg of the compound. The blend is 575 mg. Subtract, and about 7.5 mg remains for alpha lipoic acid, butcher’s broom, L-carnitine, turmeric and coenzyme Q10 together. The first ingredient is 98.7% of the blend. The 567.5 mg is a weight forced by a printed figure; the five ceilings that follow are ceilings, not amounts.
- Blend declared
- 575 mg
- Ingredients named
- Six
- Amounts printed
- One, and it is an element
- Chelate magnesium content
- 14.1% by weight
- Compound weight forced
- About 567.5 mg
- Share of the blend
- 98.7%
- Left for the other five
- About 7.5 mg together
- Tighter than position alone
- About 38 to 64 times
What a blend normally gives a reader
Start with what is actually required, because the technique below only matters against that baseline. The FDA’s labelling guidance sets out three obligations for a proprietary blend and conspicuously omits a fourth.
“You must identify proprietary blends by use of the term “Proprietary Blend” or an appropriately descriptive term or fanciful name. On the same line, you must list the total weight of all “other dietary ingredients” contained in the blend. Indented underneath the name of the blend, you must list the “other dietary ingredients” in the blend, either in a column or linear fashion, in descending order of predominance by weight.”
U.S. Food and Drug Administration — Dietary Supplement Labeling Guide: Chapter IV. Nutrition Labeling
Name the blend. Print the total weight on the same line. List the constituents underneath in descending order of predominance by weight. Nothing requires an individual amount, and Operation Supplement Safety states the consequence in one sentence: the specific amount of each ingredient “does not have to be listed”.
The descending-order rule is the only foothold, and it is a genuine one. If six items are listed heaviest first inside 575 mg, then item n cannot weigh more than 575 divided by n — because n items each at least that heavy would exceed the total. That is where the ordinary ceilings come from:
| Position | Ingredient as printed | Ordinary ceiling |
|---|---|---|
| 1 | Magnesium Glycinate | 575.0 mg |
| 2 | Alpha Lipoic Acid | 287.5 mg |
| 3 | Butcher’s Broom (Ruscus aculeatus) Root Extract | 191.7 mg |
| 4 | L-Carnitine | 143.8 mg |
| 5 | Turmeric (Curcumalonga) Rhizome Extract 95% Curcuminoids | 115.0 mg |
| 6 | Coenzyme Q 10 (as Ubiquinone) | 95.8 mg |
Look at that table as a buyer would. It permits 143 mg of L-carnitine. It permits 115 mg of a standardised turmeric extract. Every figure in it is honest arithmetic and every figure in it is, on this particular label, wrong by a factor of between thirty-eight and sixty-four. That is the problem the rest of this piece solves.
The method, in seven steps
Written to be run on any label rather than only on this one. Steps one and two are the familiar part. Step three is the move almost nobody makes, and it is the reason this label is computable at all.
- 01Write down the declared total and the countTwo figures, both printed: a Proprietary Blend at 575 mg, with six ingredients indented underneath it. Nothing in this step needs anything the manufacturer withheld, and nothing in it is controversial.
- 02Divide the total by each positionBlend constituents must be listed heaviest first, so the item in position n cannot weigh more than the total divided by n. That gives six ceilings at once. It is the familiar half of the technique and, on this label, the nearly useless half.
- 03Now look above the blend, not inside itThis is the move. Read every row that sits above the blend line and carries a percentage. Those are declared nutrients with a reference intake, and one of them may be sourced from something in the blend. On this panel there is exactly one: Magnesium 80 mg, 19%.
- 04Read the bracket beside it(as Magnesium Glycinate from proprietary blend). Three facts in five words: the figure is an element, the compound carrying it is named, and the compound is inside the blend rather than additional to it. If any one of the three were missing the method would stop here.
- 05Convert the element into the compoundA named compound has a molar mass, and therefore a fixed percentage of the element by weight. Divide the declared element by that fraction and you have the weight of the compound. There is no judgement in this step: it is division by a published constant.
- 06Subtract it from the blend totalThe compound’s weight has to be found inside the declared total, so what is left is everything else in the blend added together. This is the step that turns a list of loose ceilings into a single hard remainder.
- 07Apply the descending-order rule to the remainder, not to the wholeRe-divide: inside the remainder, item n of the ones left cannot exceed the remainder divided by n. Every figure that comes out is a ceiling and must be written as one. The first figure, the compound’s weight, is the only one that is not.
The condition for steps three to seven is precise, and it is worth memorising because it tells you at a glance whether a label can be solved. You need a declared nutrient, with a percentage beside it so you know it is the element, and a bracket naming a specific compound and placing it inside the blend. All four. Drop the percentage and you cannot be sure the figure is elemental. Drop the compound name and there is no molar mass. Drop from proprietary blend and you cannot tell whether the weight comes out of the total or sits beside it.
The same seven steps, run on this panel
Six steps rather than seven, because on this label two of them collapse into one. Every input is either printed on the bottle or published by a federal body, and the working is shown so a reader can disagree with a step rather than with a conclusion.
- 01Start with the one printed figureThe panel declares 80 mg of magnesium above the blend and says it comes from the magnesium glycinate from proprietary blend. That is an amount of the element, not of the compound.
- 02Check that the label’s own percentage agreesThe panel prints 19% of the Daily Value beside it. The NIH Office of Dietary Supplements gives the Daily Value for magnesium as 420 mg, and 80 ÷ 420 = 19.05%. The label’s arithmetic is correct, which confirms the 80 mg is elemental magnesium.
- 03Work out what the compound weighsMagnesium bisglycinate is Mg(C2H4NO2)2. Its molar mass is 172.42 g/mol, of which magnesium accounts for 24.305. The chelate is therefore 14.1% magnesium by weight.
- 04Divide80 ÷ 0.141 = 567.5 mg of magnesium glycinate. That is the weight of the first ingredient in the blend, and it is not a ceiling — it is forced by a printed figure.
- 05SubtractThe blend is 575 mg. 575 − 567.5 = 7.5 mg for alpha lipoic acid, butcher’s broom, L-carnitine, turmeric and coenzyme Q10 together. The first ingredient is 98.7% of the blend.
- 06Apply the descending-order rule to what is leftThe FDA requires blend ingredients “in descending order of predominance by weight”, so inside that 7.5 mg remainder item n cannot exceed 7.5 ÷ n: at most 7.5, 3.7, 2.5, 1.9 and 1.5 mg. Every one of those is a ceiling, not an amount.
The first bar is the one ingredient whose weight is fixed by a printed figure. The second is everything else in the blend added together. The five below it are the ceilings the descending-order rule puts on each one inside that remainder. A ceiling is a ceiling, not an amount.
The shape of the answer, in one sentence
This is a magnesium capsule with about 7.5 mg of five other things in it. The front of the bottle gives six ingredients roughly equal billing and the panel gives one of them 98.7% of the weight. Neither statement contradicts the other; the second is simply the one with arithmetic behind it.
The chemistry, slowly
The only input to this derivation that is not printed on the bottle is a molar mass, so it is worth setting out carefully rather than asserting.
Magnesium bisglycinate is a magnesium ion chelated to two glycine residues: Mg(C2H4NO2)2. Its molar mass is 172.42 g/mol. Magnesium itself accounts for 24.305 of that. So the fraction of the compound that is magnesium, by weight, is 24.305 ÷ 172.42 = 0.141, or 14.1%.
That percentage is the hinge of everything else. A supplement panel declares the element, not the compound: Magnesium 80 mg means eighty milligrams of magnesium, not eighty milligrams of magnesium glycinate. To find out how much compound is needed to carry eighty milligrams of element, divide rather than multiply:
| Step | Working | Result |
|---|---|---|
| Magnesium in the compound, by weight | 24.305 ÷ 172.42 | 0.141, or 14.1% |
| Compound needed for 80 mg of element | 80 ÷ 0.141 | about 567.5 mg |
| Share of a 575 mg blend | 567.5 ÷ 575 | 98.7% |
| Remainder for the other five, together | 575 − 567.5 | about 7.5 mg |
| Ceiling on the second-listed ingredient | the whole remainder | at most 7.5 mg |
| Ceilings on the third to sixth | 7.5 ÷ 3, ÷ 4, ÷ 5 | at most 3.7, 2.5, 1.9 and 1.5 mg |
Note what the last two rows are doing. Once the chelate is accounted for, the descending-order rule is applied again — but to the 7.5 mg remainder rather than to the 575 mg total. The second-listed ingredient could in principle be the whole remainder; the third cannot exceed a third of what is left at its position, and so on down. This is the same rule as before, run against a much smaller number.
One subtlety, stated because it is the kind of thing a careful reader will ask. The remainder divisions are indexed from the position of each ingredient within the blend as printed, which is why the third-listed ingredient is capped at 7.5 ÷ 3 rather than 7.5 ÷ 2. The ordering is the label’s own and the rule is the FDA’s; this desk has supplied neither.
Six ingredients, one weight and five ceilings
Read the first row differently from the other five. About 567.5 mg is not a ceiling: it is a weight the blend has to contain if the 80 mg declaration above it is true. The five rows below it are ceilings in the ordinary sense — upper limits, with the true amounts at or below them and possibly far below.
It is also not a measurement. Nobody weighed anything. No bottle was opened, no capsule was assayed and no Certificate of Analysis was supplied for this product. The 567.5 mg is arithmetic from a printed declaration and a published molar mass, which is a different kind of claim from a laboratory result and is weaker in exactly one respect: it describes what the label requires, not what the capsule contains.
How much tighter the mass balance is
Here are the two sets side by side. The left-hand column is what any reader gets from a 575 mg blend of six. The right-hand column is what the magnesium declaration forces. The right-hand ratio is the value of the whole technique.
| Position | Ordinary ceiling, 575 ÷ n | Mass-balance figure | Ratio |
|---|---|---|---|
| 1 · Magnesium Glycinate | 575.0 mg | about 567.5 mg — a weight, not a ceiling | — |
| 2 · Alpha Lipoic Acid | 287.5 mg | at most 7.5 mg | about 38× |
| 3 · Butcher’s Broom root extract | 191.7 mg | at most 3.7 mg | about 52× |
| 4 · L-Carnitine | 143.8 mg | at most 2.5 mg | about 58× |
| 5 · Turmeric extract, 95% curcuminoids | 115.0 mg | at most 1.9 mg | about 61× |
| 6 · Coenzyme Q10 (ubiquinone) | 95.8 mg | at most 1.5 mg | about 64× |
The ratios run from about thirty-eight at position two to about sixty-four at position six. Position one changes character rather than magnitude: under the ordinary rule it is capped at the whole 575 mg, which tells a reader nothing at all; under the mass balance it is pinned at about 567.5 mg, which tells a reader the entire shape of the product.
This is why the comparison is published rather than just the result. A reader who sees only the right-hand column might reasonably wonder whether the derivation is doing any work. The left-hand column is the alternative, and it would have permitted a sales page to imply 143 mg of L-carnitine without saying anything arithmetically false.
The same move on a label without the magnesium row
Take away the bracket and this label becomes ordinary. Six names, 575 mg, six loose ceilings, nothing else — and no way to tell a blend that is 98.7% one ingredient from one divided evenly six ways. The technique in this piece is not generally available, which is precisely why it is worth writing down when it is.
The one assumption, tested
The derivation rests on a single assumption: that Magnesium Glycinate on this label means magnesium bisglycinate, at 14.1% elemental magnesium by weight. That is the plain reading of the printed name and it is the reading this site publishes. It is still an assumption, so it is tested rather than asserted.
Some products marketed as magnesium glycinate are buffered — the chelate blended with magnesium oxide, which is far richer in elemental magnesium — and a buffered product would carry a higher percentage and therefore need less compound. The label says nothing about buffering either way. Here is the same subtraction at five percentages:
| 14.1% | 16% | 18% | 20% | 25% | |
|---|---|---|---|---|---|
| What that reading would mean | Pure magnesium bisglycinate, the plain reading of the printed name | A slightly richer chelate | A buffered blend, often cited around here | A heavily buffered blend | Richer than any glycinate this desk has seen named |
| Chelate needed for 80 mg | 567.5 mg | 500.0 mg | 444.4 mg | 400.0 mg | 320.0 mg |
| Left for the other five, together | 7.5 mg | 75.0 mg | 130.6 mg | 175.0 mg | 255.0 mg |
Read the bottom row, left to right. At the plain reading of the printed name — the first column — the other five ingredients share about 7.5 mg between them. Even at 25% magnesium — richer than any glycinate this desk has seen named — the chelate is still 320 mg of a 575 mg blend, and the other five share 255 mg between them, which at five ingredients in descending order still caps the sixth at about 51 mg. The size of the finding depends on the assumption. The direction does not.
That is what a sensitivity table is for: not to hedge a conclusion but to show how much of it survives the worst case. The worst case here is still a blend in which one ingredient takes more than half the weight, and the honest reading of the printed name gives a blend in which one ingredient takes almost all of it.
What would settle it, and who has it
A Certificate of Analysis for the lot, which reports quantities ingredient by ingredient. None was supplied for this product, and Operation Supplement Safety is blunt that laboratory testing is the only way to know what is in a bottle. The script for asking the order desk for one is published here. The lot and certificate strings on this site are draft reference strings this desk composed for that purpose and are not laboratory documents.
Why the label’s own 19% proves the reading
There is one more check, and it is the most elegant part of the whole exercise because the label performs it for you.
Everything above depends on the 80 mg being a weight of elemental magnesium rather than of the chelate. If it were a weight of the chelate, there would be about 11 mg of actual magnesium in the capsule and the derivation would collapse. So how does a reader know which it is?
The percentage. The panel prints 19% beside the 80 mg. The NIH Office of Dietary Supplements gives the Daily Value for magnesium as 420 mg for adults and children aged four and over. And 80 ÷ 420 = 19.05%, which rounds to 19. The label’s own arithmetic is correct, and a correct percentage against an elemental reference intake is only possible if the declared figure is elemental.
Had the 80 mg been a compound weight, the honest percentage would have been about 2.7% — 11.3 mg of magnesium against a 420 mg Daily Value — and the panel would have printed that instead. It did not. So this label, by getting its own sum right, has confirmed the reading that makes the rest of it computable.
A credit, stated plainly
That is a strange thing to credit a product for, and it is a credit all the same. This panel’s Daily Value arithmetic is correct, which is more than several labels in this series manage, and correct arithmetic is what makes a label reasonable to reason from. The finding that follows is unflattering; the quality of the document that produced it is not in doubt.
Six checks before publishing a derived figure
A derivation is only as good as the discipline around it. These are the six checks this desk runs before any figure on this site goes onto a page, and they are the reason the ceilings here are written the way they are.
- 01Check the label’s own percentage before you trust the rowIf the declared figure is really the element, the percentage printed beside it will agree with the published reference intake. Here 80 ÷ 420 = 19.05% against a printed 19%. If the arithmetic had not checked out, the safe reading would have been that the row means something other than what it appears to.
- 02State the assumption the chemistry rests onEvery conversion of an element into a compound assumes a formulation. Here it is that Magnesium Glycinate means magnesium bisglycinate at 14.1% magnesium, which is the plain reading of the printed name. Name the assumption on the page rather than in a footnote.
- 03Test it across a range before you publish a figureRun the same subtraction at other plausible percentages and see whether the finding survives. On this label it does: even at a richer 25% magnesium the chelate is still 320 mg of a 575 mg blend. The size of the finding depends on the assumption; its direction does not.
- 04Compare the result with the ordinary ceilingsPrint both columns. The ordinary ceilings are what any reader would otherwise have, and the comparison is the only way to show how much the technique bought. Here it is between about thirty-eight and sixty-four times.
- 05Label every figure for what it isOne weight, forced by a printed declaration. Five ceilings, forced by a rule. Nothing on the label is a measurement and nothing on it came from a laboratory. Write at most every time, because a figure stripped of its qualifier becomes a dose the moment somebody quotes it.
- 06Say what the result does not establishIt does not establish what is in the capsule — only what the label requires to be in it. It does not establish that any amount is too little to matter, which is a separate argument needing a published dose to compare against. And it says nothing at all about whether the product works.
The fifth check is the one that gets broken most often, and almost always in good faith. Somebody reads at most 2.5 mg of L-carnitine, quotes 2.5 mg of L-carnitine, and a bound produced by arithmetic has become a statement about the contents of a capsule. Nobody on this side of a laboratory is in a position to make that statement, which is why the qualifier is written every single time on this site and why this piece asks anyone quoting it to keep it.
What this does and does not establish
Four things follow from the arithmetic and three things do not, and running them together is the easiest way to overstate a good finding.
What the derivation establishes
- That one ingredient takes almost all the weight. About 567.5 mg of magnesium glycinate in a 575 mg blend, which is 98.7% of it.
- That the other five share about 7.5 mg. Together, not each. That figure is a consequence of two printed numbers and one molar mass.
- That the ceilings on those five are 7.5, 3.7, 2.5, 1.9 and 1.5 mg. Upper limits, from the FDA’s descending-order rule applied to the remainder.
- That the label’s own arithmetic is correct, and therefore that the 80 mg is elemental magnesium rather than a compound weight.
What it does not establish
- What is actually in the capsule. It establishes what the label requires. Only laboratory testing of a lot settles the rest, and no certificate was supplied.
- That 7.5 mg is too little to matter. That is a separate argument and it needs a published dose to compare against — which exists for exactly one of these five ingredients.
- Anything about whether the product works. No route of action is stated in any document supplied, and arithmetic cannot supply one.
The second item in the right-hand column is the honest limit of this piece, and it is taken up separately. For L-carnitine the comparison can be made: the NIH Office of Dietary Supplements records trials at “0.25 to 4 g/day” against a ceiling here of about 2.5 mg. For alpha lipoic acid and butcher’s broom there is no federal fact sheet at all, so no comparison is published and none will be invented. What a 7.5 mg remainder means in practice — and the half of the story that runs the other way — is the subject of a separate piece.
References
Three sources carry this piece, all opened and read: the FDA’s labelling guidance for the descending-order rule, the NIH Office of Dietary Supplements for the 420 mg Daily Value that checks the label’s percentage, and Operation Supplement Safety for what a blend is permitted to withhold.
- U.S. Food and Drug Administration (2026). Dietary Supplement Labeling Guide: Chapter IV. Nutrition Labeling.
- NIH Office of Dietary Supplements (2026). Magnesium: Fact Sheet for Health Professionals.
- Operation Supplement Safety, U.S. Department of Defense (2026). Proprietary blends: What does this mean?.
Nothing else is needed. The arithmetic uses two printed figures — 80 mg and 575 mg — one published molar mass, one published Daily Value and one sentence of FDA guidance. A reader holding the bottle can reproduce every step of it.
Read the blend row before you decide
Thirty capsules, one a day. The panel declares 80 mg of magnesium at 19% of the Daily Value, and a 575 mg blend of six ingredients. The magnesium declaration fixes the weight of the first ingredient at about 567.5 mg, which leaves roughly 7.5 mg for the other five together. No price appears anywhere but the checkout.
- Guarantee as printed at checkout
- 80 mg magnesium, 19% of the Daily Value
- Returns to 4 Times Square, Floor 22, New York, NY 10036, USA
No price appears in any document supplied to this desk, as of October 11, 2026, so none is printed here. The checkout screen is the only place a price exists. Questions first? Every published contact route is here.
Keep reading
Authorship and review
Who wrote and checked this page
What this page was checked against
- The label artwork, read at 2× and transcribed character for character. Where the label and the marketing disagree, the label is printed.
- The seller pack, quoted rather than paraphrased, and identified as marketing wherever it is used.
- The published sources listed in the references on this page. Every one was opened and read; none is cited from memory.
- The arithmetic, shown in full. Every per-ingredient figure other than the magnesium is a ceiling derived from one printed number, never a measured amount.
- Nothing else. Any fact that was not supplied is recorded as not published rather than filled in.
Last updated October 11, 2026. A highlighted slot is a value no human has supplied yet. Who reviews these pages?