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Proprietary Blend Math: How to Cap Each Ingredient on a Label
US labelling rules let a blend hide single amounts, but they require the blend total and a list in descending order by weight. So an ingredient in place k of n can hold at most the total divided by k. That gives a ceiling for every line, though never the real amount.
Written by the Prostadine label deskUpdated · 4 min read
The basics01
What does the rule say?
Under 21 CFR 101.36, a supplement may list a proprietary blend with the blend's total weight, followed by its ingredients in descending order of predominance by weight (21 CFR 101.36 (eCFR)).
So the label must tell you the total and the order, even if it does not give each amount. A blend that lists nine ingredients in order tells you the first weighs the most and the ninth the least.
From that order, a little arithmetic gives an upper bound on each line.
The evidence02
How does the cap work?
If an ingredient sits in place k, then every ingredient before it weighs at least as much. So k ingredients each weigh at least as much as this one, and together they cannot exceed the blend total. Therefore the ingredient in place k weighs at most the total divided by k.
The first ingredient has no cap except the whole blend. The second can be at most half. The third at most a third, and so on down to the ninth, which can be at most a ninth.
| Position | Largest possible share | Position | Largest possible share |
|---|---|---|---|
| 1 | 100% | 6 | 16.7% |
| 2 | 50% | 7 | 14.3% |
| 3 | 33.3% | 8 | 12.5% |
| 4 | 25% | 9 | 11.1% |
| 5 | 20% |
The numbers03
A worked example
Imagine a blend total of 1,000 mg listed in nine lines. The fifth line can hold at most 200 mg. The ninth can hold at most 111 mg. In practice the real amounts will usually be far lower for the lower lines, because the order only says each is no larger than the one before.
The numbers are invented to show the method. They are not Prostadine's figures, which are not printed. If the real blend were 200 mg, every cap would shrink in the same proportion, and the fifth line could be at most 40 mg.
That is the real lesson. The cap scales with the blend total, so the first thing to ask is the total.
The catch04
What does the cap not tell you?
It never gives the actual amount. A line can sit far below its cap. Makers sometimes put a pinch of an expensive ingredient low in the list to show its name on the front, a practice critics call label dressing.
It also says nothing about quality, potency or form. Milligrams of a raw powder and milligrams of a concentrated extract are not the same, and the rule does not distinguish them. A weight is not an activity.
And the rule applies only if the maker chooses to list a blend. A label with a proper Supplement Facts panel lists each amount, which is better.
Safety05
How does it apply to Prostadine?
The Prostadine images show no panel, and the info page lists nine ingredients without a blend total. If the formula is a blend under the rule, the order printed on the info page is nori, wakame, kelp, bladderwrack, saw palmetto, pomegranate, iodine, shilajit and neem.
That would put saw palmetto at one fifth at most and iodine at one seventh at most. Since the total is missing, even those caps cannot be turned into milligrams. Our label guide shows how to read the reply if the seller sends figures.
What to do06
What to ask the seller
- What is the total weight of the blend in a 2 mL serving?
- Is the list in descending order by weight?
- What is the amount of iodine from all sources, in micrograms?
- Can I see the Supplement Facts panel as printed on the carton?
The blend total and the iodine per serving answer most of what a doctor would need to know.
On the label07
Why does the rule exist?
It balances a maker's wish to keep a formula private with a buyer's need for some facts. The FDA allows blends because a recipe has value, and it requires the total and the order so that the buyer is not left with nothing.
It is a compromise, not a guarantee. The FTC adds a different safeguard: any health claim must have competent and reliable scientific evidence, whatever is on the label (FTC, Health Products Compliance Guidance). A hidden amount makes it hard for a buyer to check whether that standard is met.
FAQ08
Prostadine questions people ask
How does the blend ceiling work?
A group of ingredients listed under one name with a single total weight. Federal rules require the total and a list in descending order by weight, but not each amount.
How do you work out the maximum of one ingredient in a blend?
Divide the blend total by the ingredient's place in the list. The fifth of nine can be at most one fifth of the total. That is a cap, never the real amount.
Is a proprietary blend a bad sign?
Not by itself. It does make comparison with studies hard, since you cannot see doses. Ask the seller for the total and for key amounts such as iodine.
Does the order on a label always show weight?
For a listed proprietary blend, rules require descending order by weight. For a label without a panel, such as the Prostadine images, the order on the info page is a hint, not a rule.
Who wrote this09
Written and reviewed by
Pages built from the bottle photos, the info page and linked NIH, FDA, NCI, FTC and peer-reviewed sources.
Last updated . Read our editorial standards and how we check reviews. This website is run by a licensed U.S. retail desk for Prostadine, not by the manufacturer. We earn money when you buy through our order links.
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