The short answer
A proprietary blend hides the amount of each ingredient. The label gives one total weight and the names in descending order of weight, so you cannot tell whether an ingredient is there at a research dose or as a trace. US law allows this for non-nutrient ingredients [1]. EU supplement law requires each active substance in numbers [2].
What is a proprietary blend, legally?
A proprietary blend is a US labelling format set out in 21 CFR 101.36(c). The label must name the blend, list its "other dietary ingredients" in descending order of predominance by weight, and give a single number: the total weight of those ingredients. Vitamins and minerals inside a blend must still be declared one by one [1].
The format goes back to the Dietary Supplement Health and Education Act of 1994, and its purpose is to let companies protect a formula. A 2023 paper written by authors from the NIH Office of Dietary Supplements, the FDA and the industry association CHPA states the consequence plainly: the weight of the blend and the names must be declared, but not the amounts of the individual ingredients [4].
The same authors point out a second loser besides the shopper. From the label alone, nobody can calculate how much of an ingredient people actually take, and a blend label cannot be used to define a dose for a clinical trial [4]. The secrecy protects the recipe from competitors, and it keeps the recipe from you as well.
The regulation also allows the blend to be called by "other appropriately descriptive term or fanciful name" [1]. That is why blends often appear under names such as matrix, complex or system. The name is chosen by the brand. What matters is whether each ingredient underneath it has its own amount.
Is a proprietary blend allowed in the EU?
Not in its US form. Directive 2002/46/EC, the EU food supplement law, requires the amount of the nutrients or substances with a nutritional or physiological effect to be declared on the label in numerical form, per portion recommended for daily consumption [2]. Article 8 contains no exception for blends, and vitamins and minerals must also carry a %NRV [2].
Two caveats keep this honest. The directive regulates vitamins and minerals in detail, but for other substances, such as botanicals or amino acids, it leaves specific rules to national law until EU rules are adopted [2], so enforcement differs between countries. And a product bought from a webshop outside the EU may simply carry its home label, blend included.
A rule on paper is also not the same as a label in your hand. When the Belgian public health institute Sciensano bought red yeast rice supplements online, 6 of the 17 samples from an EU-based e-commerce platform had non-compliant labels: a mandatory warning was missing or incomplete, or the total amount of monacolins, the active compounds, was not stated [11].
How does a US blend label compare with an EU supplement label?
The difference sits in one row: what happens to active ingredients that are not vitamins or minerals. In a US blend they appear as names under a total. On an EU supplement label, each one should have its own amount per daily portion [1][2].
| What the label must show | US proprietary blend | EU food supplement |
|---|---|---|
| Legal basis | 21 CFR 101.36(c) [1] | Directive 2002/46/EC, Article 8 [2] |
| Vitamins and minerals | Amount of each | Amount of each, plus %NRV |
| Other active ingredients (botanicals, amino acids, caffeine) | Names only, in descending order of weight | Amount of each, in numbers |
| A single total for the mixture | Replaces the individual amounts | No blend exception in Article 8 |
What does the order of ingredients in a blend tell you?
The order gives you ceilings, never floors. Because ingredients are listed from heaviest to lightest [1], the second can be at most half of the blend, the third at most a third and the fourth at most a quarter. Only the first ingredient has a guaranteed minimum: the blend total divided by the number of ingredients.
This is arithmetic, not opinion. If the fourth ingredient weighed more than a quarter of the blend, the three above it would each weigh more still, and the four together would exceed the total. Nothing, however, stops the fourth ingredient from being a hundredth of the blend, or a thousandth.
| Position in a blend of five | Largest possible share | Largest amount in a 1,000 mg blend | Smallest possible amount |
|---|---|---|---|
| 1st | Almost 100% | Almost 1,000 mg | 200 mg (1,000 divided by 5) |
| 2nd | 50% | 500 mg | No minimum above zero |
| 3rd | 33% | 333 mg | No minimum above zero |
| 4th | 25% | 250 mg | No minimum above zero |
| 5th | 20% | 200 mg | No minimum above zero |
How small can the ingredient on the front of the pack be?
If the ingredient printed on the front sits fourth in a 1,000 mg blend, the label only promises that it weighs somewhere below 250 mg. If the first ingredient is an inexpensive bulk ingredient at 900 mg, the remaining 100 mg is shared by four ingredients, and none of them can be checked.
That gives you one test that works. Compare the ceiling with the dose used in the research the brand refers to. If the ceiling is already below that dose, the product cannot contain it, whatever the marketing says. If the ceiling is above it, you still do not know, and that uncertainty is exactly what the format is built to allow.
How common are proprietary blends?
In sports supplements, very common. Of the 100 best-selling pre-workout products analysed in a 2019 study, 58 contained at least one proprietary blend, and 44.3% of all listed ingredients across the sample had undisclosed amounts [5]. In the products with a blend, an average of 14 ingredients sat inside it without an amount [5].
Wider shelves show a lower but still large share. A survey of 1,209 unique supplements sold on two US Army installations, carried out in 2024 and published in 2026, found that 250 of them (21%) contained a proprietary blend, matrix or complex [6]. In the same survey, only 120 products (10%) carried a seal from a third-party certifier vetted by the military's supplement safety programme [6].
Do proprietary blends hide underdosing?
Often nobody can tell, and that is the problem. In the pre-workout study, the researchers could only compare doses with the research for ingredients that had a listed amount. The ingredients inside blends were out of reach [5]. Where amounts were listed, many were below research doses, which hints at the hidden ones without proving anything about them.
The disclosed numbers are telling on their own. Listed creatine averaged 2.1 g per serving, below the 3 g minimum and the 5 g standard daily dose the authors cite, and only 29% of the products reached that minimum [5]. Beta-alanine had a listed amount in 57 products, and only one of them reached the threshold the authors used for efficacy [5].
Caffeine went the other way: the average listed amount was 254 mg per serving [5]. For caffeine, a hidden amount is a safety question more than a value question. The authors warn that someone who also drinks coffee or takes an energy shot could take in high amounts of caffeine without knowing it [5].
Can an ingredient on the label be missing altogether?
Yes, and without a declared amount it is harder to catch. In a 2023 analysis of 57 US sports supplements naming one of five botanical ingredients, 23 (40%) contained no detectable amount of it [7]. For 19 of the 57, the label gave no quantity for that ingredient at all, so the researchers could not even calculate how accurate it was [7].
Only 6 of the 57 products (11%) contained a quantity within 10% of the labelled amount, and 7 (12%) contained at least one ingredient prohibited by the FDA [7]. This is label accuracy, not blend law: a declared number can be wrong too. The difference is that a number can be tested, while a name alone cannot.
The pattern repeats in other studies. None of 12 sports supplements labelled as containing the orchid Eria jarensis was accurately labelled; products listing caffeine contained between 0.1 and 665 mg per serving, and 4 contained an undeclared stimulant [8]. Of 24 products listing the stimulant higenamine, only 5 stated an amount, and none of those 5 was accurate [9].
Is a declared amount on a European product reliable?
More reliable than a name, but not automatically right. When 20 resveratrol supplements sold in Slovenia were analysed, 95% contained an amount different from the declared one, and 55% contained more than declared [12]. Declared values should be averages based on the manufacturer's analysis of the product [2].
For vitamins and minerals, the European Commission's guidance for official controls accepts a measured value in a food supplement between 20% below and 50% above the declared amount for vitamins, and between 20% below and 45% above for minerals [3]. Its supplement table covers vitamins and minerals only [3].
Does a declared extract weight tell you the dose?
Not by itself. "Extract 500 mg" gives the weight of the extract, not how much of the compound the research measured is in it. Unless the label states a standardisation, meaning a percentage of a named compound, two products with the same 500 mg can deliver very different amounts of that compound.
A survey of 17 top-selling frankincense supplements from Europe and the US found that 10 did not declare their boswellic acid content, and only 5 disclosed the species, the plant part and the boswellic acid content together [10]. A stated standardisation is a claim, not a result: one product declaring 500 mg of Ajuga turkestanica extract with 10% turkesterone contained 0.01 mg of turkesterone per serving, 0.02% of the labelled amount [7].
What should you check on a label with a blend?
Five checks take about a minute. Look for an amount next to every active ingredient, find the position of the ingredient on the front of the pack, work out its ceiling, compare that ceiling with the research dose, and check whether extracts are standardised. If a product fails the first check, the others mostly measure what you do not know.
- Is there an amount next to every ingredient that is supposed to do something? On an EU supplement label there should be [2].
- Where does the headline ingredient sit in the blend? Its ceiling is the blend total divided by its position.
- Is that ceiling below the dose used in the studies the brand points to? Then the product cannot contain that dose.
- Is an extract standardised to a named compound, with a percentage? Without it, a milligram figure is a weight, not a dose [10].
- Is there independent evidence of what is inside? Our guide to what a supplement certificate of analysis proves explains what such a document can and cannot show.
How do our own products hold up to this test?
We apply the same test to ourselves. We do not sell pre-workouts or fat burners, the product type in which the 2019 study found blends in 58 of 100 best-sellers [5]. The three products below are the ones where the comparison is sharpest, and each gives an amount for every active ingredient.
FocusFuel combines caffeine, L-theanine and vitamins B6 and B12, a combination that is often sold as a blend. Its label states 40 mg of caffeine per lozenge and, per daily serving of 2 lozenges, 80 mg of caffeine, 120 mg of L-theanine, vitamin B6 at 100% NRV and vitamin B12 at 192% NRV.
Magnesium 7 in 1 is, strictly speaking, a blend of seven magnesium compounds. For a mineral, EU law asks for the amount of the mineral itself with its %NRV [2], and the label gives it: 251 mg of elemental magnesium per 2 capsules, 67% NRV. When you compare magnesium products, compare that elemental figure, not the number of forms.
Our creatine monohydrate is a single ingredient at 5 g per serving, where listed creatine in the pre-workout study averaged 2.1 g [5]. Creatine increases physical performance in successive bursts of short-term, high intensity exercise; the beneficial effect is obtained with a daily intake of 3 g. For the wider map of label wording, see which words on a supplement label are legally defined.
Frequently asked questions
Is a proprietary blend illegal?
In the US it is legal for non-nutrient ingredients, as long as the blend is named, its total weight is given and its ingredients are listed in descending order of weight [1]. EU food supplement law requires the amount of each nutrient or physiologically active substance in numbers, and Article 8 has no exception for blends [2].
Does matrix or complex on a label mean the same as a proprietary blend?
Often it does. The US rule lets a blend carry a descriptive or fanciful name instead of the words proprietary blend [1], and a survey of 1,209 supplements counted blends, matrices and complexes together: 250 products, or 21% [6]. Check whether each ingredient under the name has its own amount.
Can I work out the amount of one ingredient in a blend?
Only its ceiling. Divide the blend total by the ingredient's position in the list: the fourth ingredient in a 1,000 mg blend weighs at most 250 mg. The first ingredient is the only one with a minimum, the total divided by the number of ingredients. Nothing sets a minimum for the others.
Is a blend always a sign of underdosing?
No. A blend can contain effective amounts; the label simply does not let you verify it. In the 2019 pre-workout study, disclosed amounts were often below research doses, with creatine at 2.1 g on average against a 3 g minimum [5], but the hidden amounts could not be assessed from the labels.
Does a declared amount guarantee what is inside?
No, but it gives you something to check. One US analysis measured 0.02% to 334% of the labelled amount [7], and 95% of resveratrol products tested in Slovenia differed from their label [12]. A declared amount can be tested against the product. A name without an amount cannot.
The bottom line
A proprietary blend gives you names and a total, and withholds the one number that decides whether an ingredient can do anything: its dose. The order of the list sets only ceilings. Under EU supplement law every active substance should carry an amount per daily portion [2], so a blend on a European label is a reason to ask questions, and a declared dose is the least you should expect.
This article is general information, not medical advice. Food supplements should not be used as a substitute for a varied, balanced diet and a healthy lifestyle.
Sources
- 21 CFR 101.36, Nutrition labeling of dietary supplements (paragraph c, proprietary blends). Electronic Code of Federal Regulations, current text.
- Directive 2002/46/EC of the European Parliament and of the Council of 10 June 2002 on the approximation of the laws of the Member States relating to food supplements (Articles 2, 8 and 9, recital 8). Official Journal of the European Communities, 2002.
- European Commission. Guidance document for competent authorities for the control of compliance with EU legislation with regard to the setting of tolerances for nutrient values declared on a label (section 4, table 2). 2012.
- Saldanha LG, Dwyer JT, Hardy CJ, MacKay DJ. Perspectives on the Use of Proprietary Blends in Dietary Supplements. The Journal of Nutrition, 2023.
- Jagim AR, Harty PS, Camic CL. Common Ingredient Profiles of Multi-Ingredient Pre-Workout Supplements. Nutrients, 2019.
- Clegg KE, Whitbeck KM, Brennan JD, Beymer MR. Quality Improvement Project to Assess the Safety of Dietary Supplements Sold on Two United States Army Installations, 2024. Military Medicine, 2026.
- Cohen PA, Avula B, Katragunta K, Travis JC, Khan I. Presence and Quantity of Botanical Ingredients With Purported Performance-Enhancing Properties in Sports Supplements. JAMA Network Open, 2023.
- Cohen PA, Abarca R, Sovereign A, Gonzaga MJ, Gerona R. Presence and quantity of ingredients in sports supplements purportedly containing the orchid Eria jarensis. Clinical Toxicology, 2025.
- Cohen PA, Travis JC, Keizers PHJ, Boyer FE, Venhuis BJ. The stimulant higenamine in weight loss and sports supplements. Clinical Toxicology, 2019.
- Meins J, Artaria C, Riva A, et al. Survey on the Quality of the Top-Selling European and American Botanical Dietary Supplements Containing Boswellic Acids. Planta Medica, 2016 (three co-authors work for an extract manufacturer).
- Vanhee C, Jacobs B, Canfyn M, et al. Quality Control and Safety Assessment of Online-Purchased Food Supplements Containing Red Yeast Rice (RYR). Foods, 2024.
- Bensa M, Vovk I, Glavnik V. Resveratrol Food Supplement Products and the Challenges of Accurate Label Information to Ensure Food Safety for Consumers. Nutrients, 2023.
