A proprietary blend is a group of ingredients disclosed on a Supplement Facts panel as a single combined weight, with the individual amounts withheld. It is legal, it is common, and it is the single largest blind spot on a supplement label.
What the rule actually requires
For a proprietary blend, the manufacturer must disclose two things: the total weight of the blend, and the ingredients in descending order by weight.
That is the whole requirement. The amount of each individual ingredient can be omitted.
So a label reading:
Proprietary Sleep Matrix — 1,200 mg Valerian root, passionflower, chamomile, melatonin
tells you truthfully that there is more valerian than passionflower, more passionflower than chamomile, and more chamomile than melatonin. It is entirely consistent with that blend containing 1,190 mg of valerian and roughly ten milligrams split across the other three.
Why this matters more than it sounds
The pattern the disclosure rule permits is sometimes called fairy dusting: including a scientifically interesting ingredient in an amount far below any studied dose, so it can appear on the label and in the marketing without meaningfully contributing to the product.
The order requirement is a real constraint and it is worth using. If the ingredient the entire advertisement is built around appears last in a four-item blend, you know it is the smallest component by weight. That is often enough to make a decision.
The legitimate case for blends
It would be unfair to treat every proprietary blend as concealment. The stated rationale — protecting a formulation from being copied by a competitor — is real, and formulation work does represent genuine investment.
The problem is that the disclosure rule cannot distinguish between a company protecting real work and a company hiding an underdosed formula. Both look identical on the panel. So the burden lands on the buyer, and the reasonable response is not to assume bad faith, but to note that you have been given less information and to weight the product accordingly against a competitor that disclosed fully.
A practical rule
When comparing two products, treat full per-ingredient disclosure as a feature you are willing to pay for. A company that publishes exact amounts is inviting you to check its doses against the literature. A company that does not has declined that invitation, whatever its reason.
If you want to go one step further, third-party testing answers a different question again: not what the label claims, but whether the capsule matches it.
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