"Third-party tested" is easy to print and hard to fake. Here is how to tell a properly, independently checked supplement from a hollow marketing claim.
Key Takeaways
Third-party testing means an independent laboratory, not the brand, checks a product against a defined standard and reports what it finds.
It matters because in the UK supplements are regulated as food, not medicine, so no product-by-product approval checks purity before sale.
Look for a named, recognised certifier: Informed Sport is the mark most trusted by UK athletes, with the Cologne List widely used across Europe.
Always confirm the claim on the certifier's public register for the exact product or batch; a mark you cannot verify is just a logo.
Be sceptical of vague "tested" or "lab tested" language with no named certifier and no way to check it.
Evan Lynch is a CORU-registered dietitian with a BSc in Food Science and Health, a Postgraduate Diploma in Dietetics, and an MSc in Sports Nutrition. Evan is the Head of Nutrition for Europe at AG1, where he supports strategic nutrition direction, education, and evidence-based communication. Alongside this role, he runs a private practice supporting clients across sports nutrition, gastrointestinal disorders, geriatric nutrition, and weight management.
That gap, between the phrase and the proof, is what this guide is about. Checking a supplement takes no special expertise once you know where to look. Ahead: what third-party testing actually means and why it matters, which certifications carry weight, where a mark sits on the label, how to confirm it on the certifier's own register, and how to spot a hollow "tested" claim hoping you will not look.
Every reputable brand runs some testing of its own. Third-party testing is a different animal. An independent laboratory, with no stake in sales, checks the product against a defined standard and reports what it finds. That independence is the entire point. The company is not marking its own homework.
Good programmes usually verify two things. One, that what is on the label is actually in the tub, at the dose stated. Two, that nothing is in there that should not be, whether heavy metals, microbial contamination or substances banned in sport. The strongest programmes do both, test against a published standard, and let anyone look up the result on a public register.
Because in the UK, supplements are regulated as food, not as medicines. Under food law, overseen by the Food Standards Agency,⊕ products have to be safe and honestly labelled, but nothing resembling medicine-style approval checks the safety and purity of each individual product before it reaches a shelf. That responsibility falls mostly to the manufacturer.
Most brands take it seriously. Not all. Independent analyses have turned up product after product that is mislabelled, under- or over-dosed, or carrying things it should not, undeclared pharmaceuticals among them.⊕ That is why third-party testing exists in the first place. It closes the gap between "trust us" and "here is the proof", and it matters for everyone, most of all for anyone who is pregnant, managing a health condition, or bound by anti-doping rules, where an unexpected ingredient is a good deal more than an inconvenience.
A handful of marks earn their place. These are the ones worth learning to recognise:
Informed Sport. This is the mark UK athletes and governing bodies trust most. Run by the testing laboratory LGC, Informed Sport checks supplement products batch by batch for substances banned in sport, screening against the kind of prohibited list the World Anti-Doping Agency maintains, using accredited laboratory methods. Every certified batch goes up on a searchable online register you can check yourself.⊕ Its sister programme, Informed Choice, applies similar batch testing for the wider consumer market.
The Cologne List (Kölner Liste). A long-running anti-doping initiative run with the Center for Preventive Doping Research at the German Sport University Cologne. It screens supplements for doping-relevant substances, with a particular eye on anabolic steroids and stimulants, and publishes the results in a searchable database.⊕ It is used widely across Europe and is folded into the German National Anti-Doping Agency's prevention network, which makes it a handy reference for European shoppers.
Start with the packaging. Certification logos tend to sit on the front of the pack or near the ingredients panel on the back, and some products also print a batch number tied to a specific test.
Then do the bit most people skip. Confirm it. Every credible certifier keeps a searchable public register, so this part is quick.
1. Note the certifier named on the label (Informed Sport, the Cologne List, NSF and so on), the exact product name, and the batch number if there is one.
2. Go to that certifier's own website and find its product register or search tool.
3. Search for the product, and the batch if it is listed. A certified product shows up in the register. If it does not, the mark does not hold, however convincing the logo looks.
The whole thing takes a minute or two, and it is the single most useful habit a supplement shopper can build.
Not every reassuring phrase carries weight. The warning signs are fairly consistent. The claim names no certifier: "third-party tested" or "lab tested" with nobody attached tells you nothing about who did the testing, or against what standard. There is nothing to verify, because there is nothing to look up. A brand's own certificate of analysis is worth reading, but it is not the same as independent certification, and the line between the two gets blurred on purpose more often than you would like. Be wary, too, of language that borrows the sound of certification, such as "clinically formulated" or "purity guaranteed", without pointing at an independent standard. If the product is nowhere on a certifier's register, treat the claim as marketing until something proves otherwise.
A short routine covers almost everything:
Once you are confident a product is what it says it is, the more useful question becomes whether you need it at all. We work through that with Dr Rangan Chatterjee in Which Supplements Should I Take?.
Third-party testing is among the clearest quality signals a supplement can carry, but only when it is verifiable rather than decorative. The words on their own cost nothing. What counts is a named, independent certifier, a published standard, and a register you can check in a couple of minutes. Learn to tell a logo from a verified claim, and you can shop with a good deal more confidence and a good deal less blind trust.
No, and this is the most common mix-up. Third-party testing confirms that what is on the label is in the tub, and that unwanted contaminants are not, but it says nothing about whether the product does anything useful for you. A supplement can be immaculately tested and still be something you do not actually need.
Some are and some are not, so the mark matters more than the category. AG1, for example, is certified by Informed Sport and the Cologne List and batch-tested in independent labs for banned substances and contaminants,⊕ which you can confirm on the certifier's public register. Whichever product you are weighing up, check the register for that specific item rather than taking the front of the pack on trust.
Work backwards from the certifiers. Informed Sport, the Cologne List and NSF each keep a searchable public register, so you can look up whether a given product carries their mark and confirm a specific batch in a minute or two. It is a far more reliable route than trusting a "tested" claim printed on the front of a tub.
NSF certification. In the United States, NSF runs the equivalent schemes. NSF Certified for Sport screens for more than 280 substances banned in sport and confirms label accuracy,⊕ while the broader consumer mark certifies against the dietary-supplement standard NSF/ANSI 173.⊕ Both carry weight, though they speak more to shoppers in the US than in the UK.
The thread running through all of them: each is run by an independent organisation, tests against a published standard, and lets you check a given product yourself. A mark you cannot verify is just a logo.
