Flip over a supplement bottle and you'll usually find one of two label formats. Either every ingredient is listed with its own per-serving dose in milligrams, or a group of ingredients is listed under a name like "Proprietary Blend" or "Complex," followed by a list of ingredient names and a single combined weight for the whole group. Our desk gets questions about what that second format actually discloses, so here's the general, non-product-specific breakdown of what a proprietary blend does and doesn't tell you, and what U.S. labeling rules actually require.
The Bottom Line
Proprietary blends are legal — federal labeling rules for dietary supplements explicitly allow them. A manufacturer must list every ingredient in the blend, in descending order by weight, and disclose the blend's total combined weight. What the rule does not require is disclosure of how much of that total weight belongs to any individual ingredient. That matters because clinical research is almost always conducted on one specific ingredient at one specific dose — with a proprietary blend, there is no way to know from the label alone whether the ingredient you're interested in is present anywhere near a dose that research has actually studied.
What each format actually shows you
A fully disclosed formula lists each ingredient on its own line with its own milligram (or microgram, or gram) amount. That lets you directly compare what's in the product to what's been studied in published research on that specific ingredient — if a study used 500mg of an ingredient and the label says the product contains 500mg of it, that's a straightforward comparison.
A proprietary blend works differently. Federal regulation (21 CFR § 101.36) requires that dietary ingredients inside a proprietary blend be declared in descending order of predominance by weight, and that the blend carry a single quantitative amount representing the total combined weight of every ingredient in it. So a blend might read: "Proprietary Blend 1,200mg: Ingredient A, Ingredient B, Ingredient C" — with no way to know from the label how those 1,200 milligrams are actually split between the three.
Why the comparison problem is real, not theoretical
Because the ingredients are listed in descending order by weight, the first-listed ingredient in a blend is, by definition, present in the largest amount — but "largest amount within this blend" doesn't tell you what that amount actually is in milligrams, or whether it's anywhere close to a dose used in the research behind that ingredient's reputation. A blend can legally list a headline ingredient first while that ingredient makes up a small fraction of the blend's total weight, with a cheap bulking or filler ingredient — listed further down, in a smaller amount than the headline ingredient by definition — nonetheless accounting for most of the blend's actual weight. There is no way to rule that scenario in or out from a proprietary blend label alone; it depends entirely on the true, undisclosed breakdown.
This connects directly to how supplement research is done. Clinical studies test a specific ingredient at a specific, defined dose — not a philosophy or a category of ingredient. If a product buries that ingredient in an undisclosed blend, there's no way to verify from the label whether the dose in your bottle bears any resemblance to the dose that was actually studied.
The real regulatory picture
It's worth being precise here: proprietary blends are not a labeling loophole or a violation — they're an explicitly permitted labeling format under FDA's own dietary supplement nutrition-labeling regulation. The rule requires full disclosure of which ingredients are present and their relative order by weight, plus the blend's total weight, which is real transparency, just not complete transparency. What it does not require — and this is the part that's easy to miss — is the individual quantity of each ingredient inside that blend. Manufacturers who use blends are typically doing so to protect a specific formulation ratio from competitors, which is a legitimate business reason; it just comes at the cost of the consumer's ability to verify individual dosing.
What's actually worth checking
- Does the label list every ingredient with its own individual dose, or are some ingredients grouped under a blend name with only a combined total?
- If it's a blend, is the ingredient you actually care about listed first (largest share) or further down the list (smaller share, by definition, than whatever precedes it)?
- Does the total blend weight even leave room for a research-comparable dose of every listed ingredient? Sometimes basic arithmetic — total blend weight divided among however many ingredients are listed — makes clear that at least some of them can only be present in small amounts.
- Has the company published the individual amounts anywhere else — a website, a certificate of analysis, direct correspondence — even though the label itself doesn't require it?
Sources
- Electronic Code of Federal Regulations, 21 CFR § 101.36 — Nutrition labeling of dietary supplements
- Council for Responsible Nutrition, "Proprietary Blends in Dietary Supplements"
- Federal Trade Commission, "Health Products Compliance Guidance" (December 2022)
- U.S. Food and Drug Administration, "Questions and Answers on Dietary Supplements"