How to read a supplement label — and see through the claims
%NRV, permitted versus dubious health claims, fillers and "proprietary blends". A plain-English guide to working out what's actually in the tub — and what the marketing is hoping you won't notice.
In Great Britain, food supplements are regulated as food, not medicine. They cannot legally claim to prevent, treat or cure any disease — that's reserved for licensed medicines under the MHRA. Since 1 January 2021, only wording listed on the GB Nutrition and Health Claims (NHC) Register may be used, and every label must carry a note that supplements are "not a substitute for a varied and balanced diet and a healthy lifestyle." If a product promises more than that, the claim — not your health — is the problem.
Label red flags — what should make you pause
None of these is illegal on its own, but together they're how a weak or overhyped product hides in plain sight. Run any tub past this list.
"Proprietary blend" with no individual doses
A group of ingredients given one combined weight, so you can't see how much of each you're getting. It lets a brand list impressive-sounding extracts at "fairy-dust" doses while padding the rest with cheap filler. Prefer labels that state the amount of every active ingredient.
No %NRV shown for vitamins and minerals
For the 13 vitamins and the minerals with a set Nutrient Reference Value, the label should give the amount per daily dose and the %NRV. Its absence — or a figure buried off-pack — makes it hard to compare strength or spot a token dose.
Disease promises, even implied
"Beats colds", "eases anxiety", "clears joint pain" — the ASA treats these as prohibited medicinal claims. Authorised wording is more modest, e.g. a nutrient that "contributes to the normal function of the immune system."
Mega-doses framed as "high strength"
More isn't automatically better, and some nutrients have a safe upper limit. The NHS advises no more than 100µg (4,000 IU) of vitamin D a day for adults; "5,000 IU" on the front is a marketing number, not a health one.
A long "other ingredients" list you can't read
Bulking agents, anti-caking agents and coatings aren't sinister in themselves, but a tub that's mostly excipients around a tiny active is poor value. Check what's carrying the dose.
Testimonials doing the heavy lifting
"I haven't been ill since!" quotes are used precisely because the brand can't make the claim itself. A review quoting a cure is the same prohibited claim in a customer's mouth.
Claim types — what's allowed, what isn't
Three tiers of wording you'll meet on packs and ads. Knowing which is which tells you instantly whether a brand is playing within the rules.
| Claim type | What it sounds like | Status | What to do |
|---|---|---|---|
| Authorised health claim | "Vitamin C contributes to normal immune function" | Permitted if on the GB NHC Register and the product meets the minimum nutrient level | Fine — but check the nutrient is actually present in a meaningful amount |
| Nutrition claim | "High in fibre", "source of iron" | Permitted if defined criteria are met | Reasonable; verify against the %NRV on the back |
| Medicinal / disease claim | "Treats colds", "lowers blood pressure", "cures eczema" | Prohibited for supplements — medicines only | Treat as a serious warning sign about the whole brand |
| Vague "structure-function" puffery | "Supports wellness", "boosts vitality" | Not on the register; allowed only as non-specific puff alongside a real authorised claim | Ignore it — it means nothing measurable |
Based on retained EU Regulation 1924/2006, the GB NHC Register and CAP Code section 15. Botanical ("herbal") claims largely remain "on hold" pending review.
How to read a tub in two minutes
A quick, repeatable routine for the supermarket aisle or a checkout page.
Find the active dose
Look for the amount per daily serving of the ingredient you actually want — not the blend total, not the front-of-pack headline.
Check the %NRV
For vitamins and minerals, see what share of the reference intake one dose gives. Very low or wildly over 100% both deserve a second look.
Read the "other ingredients"
Scan the fillers, coatings and anti-caking agents. Fine in small amounts; a red flag if they dwarf the active.
Test the claims
Mentally sort each promise into authorised, nutrition, or prohibited. Any disease claim sinks the brand's credibility.
Sense-check against need
Most people eating a varied diet don't need most supplements. The main UK-wide exception is vitamin D in autumn and winter — see the NHS guidance.
"Proprietary blends": the honest balance
- Occasionally protect a genuinely novel formulation recipe
- Can simplify a very long ingredient list on a small pack
- Hide the individual dose of every ingredient, so you can't judge strength
- Let brands list trendy extracts at amounts far below any useful level
- Make like-for-like price and potency comparison impossible
- Are frequently used to disguise cheap filler as a premium formula
Reading labels: your questions
What does %NRV actually mean?
Nutrient Reference Value is the daily amount of a vitamin or mineral considered enough for an average adult. The %NRV tells you what share of that one dose of the product provides — so 100% iron means a full reference day's worth. It's the quickest way to compare two products' real strength, and UK labels must show it for vitamins and minerals with a set NRV.
Is a higher %NRV always better?
No. For most nutrients, hitting around 100% of the NRV is plenty if your diet is short. Some nutrients have safe upper limits — for example, the NHS advises adults take no more than 100µg (4,000 IU) of vitamin D a day. "Mega-dose" framing is usually marketing, and occasionally a genuine safety concern. If in doubt, ask a pharmacist.
Are fillers and additives dangerous?
Almost always no. Bulking agents, anti-caking agents and coatings are permitted food additives used to make tablets hold together and flow through machines. The issue is rarely safety and usually value: a tub that's mostly excipient around a token active is poor value, not poisonous.
Why can't a supplement say it cures something?
Because legally it's a food, not a medicine. Only licensed medicines, regulated by the MHRA, may claim to prevent, treat or cure disease. The ASA has ruled even softer wording — "I don't get sick", "my pain disappeared" — as prohibited disease claims. Seeing them is a reason to distrust the seller.
Do I even need supplements?
For most people eating a varied, balanced diet, no — and labels must say as much. The main UK-wide exception is vitamin D, which the NHS suggests everyone consider during autumn and winter. For anything tied to a personal health concern, speak to your GP or pharmacist rather than self-prescribing from a label.
Choose with your eyes open
This guide is educational, not medical advice. For decisions about your own health, your GP, pharmacist or the NHS should always come first. For checking labels and claims, our other consumer guides are a good next step.