An unexpected reaction to something you bought over the counter usually just gets shrugged off as "it didn't agree with me." The UK has a formal pharmacovigilance system for exactly this — but knowing which product types it covers matters, because not everything sold as a "supplement" falls under the same regulatory umbrella.
What the Yellow Card scheme actually covers
The Yellow Card scheme, run by the Medicines and Healthcare products Regulatory Agency (MHRA), collects reports of suspected side effects for medicines and vaccines (prescription and over-the-counter), licensed herbal medicines and homeopathic remedies, medical devices, e-cigarettes, and blood products. It was established in 1964 following the thalidomide crisis and remains the UK's core early warning system for medicine safety.
Here's the important nuance: a licensed herbal medicine (one with a Traditional Herbal Registration or full marketing authorisation) clearly falls under Yellow Card. A plain multivitamin, protein powder, or generic "wellness" capsule sold as a food supplement is legally regulated as food in the UK, not as a medicine — so while you can still submit a Yellow Card report if you suspect an interaction with a medicine or a genuine safety concern, a straightforward contamination or mislabeling issue with an ordinary food supplement is also worth reporting to your local authority's Trading Standards or Environmental Health team, which handles food safety enforcement, alongside Yellow Card.
How to actually file a report
- Go to yellowcard.mhra.gov.uk (or use the Yellow Card app) and search for the specific product — if it's not listed, there's an option to submit details manually.
- Describe the suspected reaction as specifically as possible: what happened, how severe it was, and whether it required medical attention.
- Include the product's licence or batch number if visible on the packaging — this helps MHRA trace the exact manufacturing batch.
- Submit — reports feed into MHRA's ongoing safety monitoring and can contribute to safety warnings or, in serious cases, product withdrawal, when a pattern emerges across multiple reports.
If it's a food supplement issue specifically
For contamination, undeclared ingredients, or counterfeit products sold as ordinary food supplements (not licensed medicines), also report to your local council's Trading Standards service — food supplement safety and labelling enforcement sits with them and the Food Standards Agency, not exclusively with MHRA.
🔎 Worried about what's in the bottle? Check your own supplement's ingredients with our free Supplement Ingredients Auditor →, and track whether it's actually working (or causing reactions) with our free Supplement Tracking Diary →.
See also: in the US, the equivalent route is reporting to the FDA via MedWatch.