The honest way to read a supplement label is to ignore the front of the pack entirely and go straight to the ingredients panel and nutrition table on the back – that’s where you find out what you’re actually buying, and it’s also where most of the tricks live.
Serving size versus container size
The first number to check is the serving size, not the total amount in the tub or box. A “5000mg per serving” claim on the front can quietly mean two scoops, not one, or a serving that’s twice what most people actually take. Always look at how many servings the container provides and divide the price by that number, not by the container size, to get a real cost per dose. This trick shows up constantly with protein powders and greens blends, where a “30 servings” claim sometimes assumes a scoop size smaller than what most people actually use, quietly turning a month’s supply into three weeks.
- Check servings per container, not just the headline dose on the front of the pack.
- Compare products on cost per serving at the labelled dose, using our cost calculator if you want to do this quickly across brands.
Percentage reference intake (%RI / NRV)
Vitamin and mineral amounts are usually shown alongside a percentage – “%RI” in the EU or “%NRV” on older labels – meaning the percentage of the Reference Intake (or Nutrient Reference Value) an adult typically needs per day. A product showing “1000% RI” of a vitamin isn’t automatically dangerous, since many water-soluble vitamins have wide safety margins, but it’s worth knowing what the number means rather than assuming bigger percentages are automatically better. For a nutrient like vitamin D, exceeding recommended upper intakes over long periods is a real consideration, not just a rounding curiosity.
- %RI tells you the dose relative to an average adult’s daily need – it does not tell you whether more is useful for your specific goal.
- Fat-soluble vitamins (A, D, E, K) build up in the body more than water-soluble ones, so treat very high %RI figures on these with more caution.
Active dose versus “proprietary blend” tricks
This is where labels get genuinely misleading. A “proprietary blend” or “complex” lists several ingredients together with only a single combined weight, not individual doses. That means a blend could be almost entirely one cheap filler ingredient with just a token amount of the expensive, evidence-backed ingredient you actually bought the product for – and you have no way to tell from the label alone.
- Individually-dosed labels are the honest format – each active ingredient gets its own listed milligram amount.
- Proprietary blends hide the split between ingredients, which is exactly the point from a cost-cutting perspective.
- If a product won’t tell you the exact dose of its main active ingredient, treat that as a warning sign, not a trade secret worth respecting.
Spotting underdosed ingredients
Even with individual doses listed, a label can include an ingredient at a dose far below what clinical studies actually used – just enough to put the name on the box. This is common with ingredients like creatine, beta-alanine, or various “adaptogens” added at token amounts inside multi-ingredient formulas.
- Compare the labelled dose to the amount used in research for that ingredient before assuming it will do anything at that level.
- Single-ingredient products (plain creatine, plain caffeine, plain whey) make this comparison far easier than multi-ingredient blends.
- See our pre-workout guide for how this plays out in stimulant blends specifically.
EU versus US labelling differences
EU labels must show nutrition information per serving and often per 100g/100ml, using %RI values set by EU regulation, and any health claim on the pack must be one specifically authorised in the EU register. US labels use a “Supplement Facts” panel with %Daily Value figures based on different reference amounts, and US rules allow broader “structure/function” claims (like “supports immune health”) that would not be permitted under EU health-claim rules without formal authorisation. If you’re buying from abroad, don’t assume a claim legal on a US label would be legal – or necessarily accurate – on an EU one.
What “high in” and other claims legally mean
Terms like “source of” and “high in” aren’t just marketing flourishes in the EU – they’re legally defined. “Source of” a vitamin or mineral generally requires at least 15% of the reference intake per serving, while “high in” requires at least twice that, around 30%. A genuine EU-authorised health claim (for example, that protein contributes to the maintenance of muscle mass, or that vitamin D contributes to the maintenance of normal muscle function) can only be used if the product meets the conditions attached to that specific claim in the register – it isn’t something a brand can just decide to print.
Putting it together: a quick checklist
Before buying, run through a short list: check the actual serving size and servings per container; look for individually-dosed ingredients rather than a blend hidden behind one combined weight; compare doses against amounts used in real studies where you can; note whether health claims on the pack are the specific authorised wording rather than vague benefit language; and work out a genuine cost per serving rather than trusting the price on the front of the box. None of this takes more than a minute once you know what to look for, and it’s the difference between paying for an effective dose and paying for a label. It’s also worth remembering that a well-formulated label with honest doses and clear individual ingredients is a genuine positive sign about a brand – it costs a company nothing to be transparent about what’s actually inside, and brands that hide behind blends usually have a reason to.
Source: EU Register of nutrition and health claims, NHS – Vitamins and minerals.
Frequently asked questions
What is a proprietary blend and why is it a red flag?
A proprietary blend lists several ingredients together under one combined weight instead of individual doses. That means most of the blend could be a cheap filler with only a token amount of the ingredient you actually wanted, and there is no way to tell the split from the label alone.
What does %RI or %NRV mean on a supplement label?
%RI (Reference Intake) or %NRV (Nutrient Reference Value) shows the percentage of an average adult's estimated daily need for that vitamin or mineral provided by one serving. A high percentage isn't automatically dangerous, but it's worth checking rather than assuming a bigger number is simply better, especially for fat-soluble vitamins like A and D.
How do I know if a supplement dose is actually effective?
Compare the labelled dose per serving to the amount used in clinical studies on that specific ingredient. Single-ingredient products make this easy to check; multi-ingredient blends, especially proprietary blends, often make it impossible to know the exact dose you're getting.
What is the difference between EU and US supplement labels?
EU labels use %RI values and can only carry health claims specifically authorised in the EU register. US labels use %Daily Value and allow broader 'structure/function' claims that would not meet EU health-claim rules, so a claim legal on a US label is not automatically accurate or legal on an EU one.
What does 'high in' or 'source of' legally mean on a label?
In the EU these are defined terms, not just marketing language. 'Source of' a vitamin or mineral generally requires at least 15% of the reference intake per serving, and 'high in' requires at least twice that, around 30%, before a brand is allowed to use the wording.