Supplements aren’t regulated like medicines — so what actually guarantees the label matches the contents? Independent testing. Here’s how it works and what to look for.
In the UK and EU, supplements are regulated as food, not medicines. Manufacturers are legally responsible for making products that are safe and accurately labelled — but there’s no pre-market approval of every batch the way there is for drugs. Independent testing exists to close that trust gap, because surveys have repeatedly found products that under-deliver, over-deliver, or contain unwanted contaminants.
A COA is a lab report for a specific batch. It covers two things you care about: identity and potency (does it contain what the label says, at the stated amount?) and purity (is it free from meaningful levels of heavy metals, microbes and other contaminants?). Ideally that testing is done by an accredited, independent laboratory.
Several independent programmes put a mark on products that pass their checks — for example NSF, Informed Sport (which screens for substances banned in sport, useful for athletes) and USP. Each verifies slightly different things, but all signal that someone other than the brand has looked inside the bottle.
Finally, look for GMP. Making a product in a GMP-certified facility means it’s produced to consistent, controlled quality and hygiene standards — the foundation that testing then verifies. UK manufacturing to these standards is a quiet but meaningful quality signal.
Because supplements are regulated as food, independent testing is your best assurance the label matches the bottle. Look for batch testing or a Certificate of Analysis, GMP manufacturing, and recognised third-party marks.
It means an independent laboratory — one with no financial stake in the brand — has checked a finished batch against its label for identity, potency and contaminants. In other words, someone other than the manufacturer marks the homework, which is what makes the result worth trusting.
A COA is the batch-specific paper trail behind a testing claim. It records what was tested, the methods used, and the results — heavy metals, microbes, and the actual measured amount of each active versus what the label promises. No COA, no proof.
Ask for the COA covering your specific batch or lot number, check whether every batch is tested rather than the occasional spot check, and look for a dedicated quality page. A brand that can’t produce one when asked is telling you something.
Being honest about the limits: testing confirms the contents match the label and are free of contaminants. It doesn’t, on its own, prove a product is effective or right for you — that still comes down to the right ingredient at the right dose.
Manufacturers are legally responsible for safety and accurate labelling, but independent third-party testing provides extra, unbiased verification of potency and purity.
A document from a laboratory confirming a batch's identity, potency and purity, including tests for contaminants such as heavy metals.
Good Manufacturing Practice: a certified standard for making products consistently and hygienically to controlled quality specifications.
No — it’s voluntary. That’s precisely why it’s a meaningful signal: a brand that pays for independent testing is choosing accountability it didn’t have to.
Typically heavy metals such as lead, arsenic, mercury and cadmium, plus microbial contamination and — where relevant — pesticide residues and banned substances.
The strongest brands test every production batch rather than occasionally, so each lot that reaches you has its own verification.
No — brand size isn’t proof. Ask for the COA regardless of how familiar the name is; paying more for a logo is a separate thing from paying for testing (see the brand tax).