Iga Świątek, a contaminated melatonin, and what Informed Sport actually prevents

On 28 November 2024 the International Tennis Integrity Agency announced a one-month suspension for Iga Świątek, who had been the world No. 1 in August 2024 when the sample was collected. The substance found was trimetazidine (TMZ), a Hormone and Metabolic Modulator on the WADA Prohibited List (category S4, specifically S4.4), banned both in and out of competition.

The source identified and accepted by the ITIA was a regulated, non-prescription melatonin medication, manufactured and regulated in Poland — an unremarkable, pharmacy-class product rather than a sports supplement. That is the unusual feature of the case. The contamination was not in a pre-workout or a fat-burner picked up from an internet retailer. It was in something a thousand non-athletes might take to help them sleep, available through pharmacies and bought on the kind of assumption most consumers make about a regulated medicine.

Strict liability is what does the damage

The WADA Code holds an athlete responsible for any banned substance found in their body, regardless of how it got there. Świątek met the ITIA standard for “No Significant Fault or Negligence” and her fault was placed at the lowest end of the range — that reduces the sanction; it does not erase it. The practical cost is what matters: the provisional suspension ran from 12 September to 4 October 2024 and cost her three Asian-swing events — the Korea Open, the China Open, and the Wuhan Open — along with the ranking points and prize money attached, plus the time and expense of identifying and chemically analysing the source.

This is not a one-off

Athletes who eventually clear their names in contamination cases do so by identifying and chemically analysing the source — at considerable cost and reputation damage along the way. Two recent tennis examples make the pattern visible.

• Simona Halep (2022). Tested positive for roxadustat at the 2022 US Open; originally banned for four years by an independent tribunal in September 2023; reduced to nine months on appeal at CAS in March 2024 after the panel accepted the source was a contaminated collagen supplement.
• Jannik Sinner (2024). Twice positive for clostebol in March 2024, traced to Trofodermin — a clostebol skin spray sold over the counter in Italy — applied by his physiotherapist to a cut finger and then handled Sinner without gloves. Initially cleared by an independent tribunal in August 2024 (“no fault or negligence”); WADA appealed, and the case settled on 15 February 2025 at a three-month ban under a case-resolution agreement, served from 9 February to 4 May 2025.

Sinner’s vector was a topical cream rather than a supplement, but the strict-liability principle is the same.

What Informed Sport actually does about this

Informed Sport is a UK-run programme operated by LGC. It tests every batch of a certified product against the WADA Prohibited List in an ISO/IEC 17025-accredited laboratory, which is what makes it useful as a contamination check rather than a manufacturing audit alone. The accompanying site assessment specifically targets cross-contamination from shared production lines — a known route by which a clean ingredient picks up traces of a banned substance from equipment that previously handled one. Informed Sport is the every-batch tier of the LGC programme, and is distinct from Informed Choice, which is sample-based.

The honest caveat

Informed Sport does not certify pharmacy-class products like the melatonin in Świątek’s case — those sit outside the scheme entirely. So this is not a story about Informed Sport catching the contamination that the ITIA found. It is a story about how strict liability works in practice and how asymmetric the consequences are. Where an athlete does have a choice — sports nutrition categories such as protein, pre-workouts, electrolytes, BCAAs, and recovery products — batch-tested certification is the only proactive check that exists, and the gap between contamination probability (low) and career consequences (significant) makes that choice clear-cut.

Practical takeaway

For a UK athlete subject to testing, the rule in the covered categories is straightforward: take only Informed Sport-certified products, and verify the lot code at sport.wetestyoutrust.com. The specific lot printed on the bottle has to map to a result in the database; a brand listed in the directory without the matching lot is not enough, because the certification attaches to a batch rather than to the brand. UKAD’s own “Managing Supplement Risks” guidance points the same way: it directs athletes to use only batch-tested products and to verify the actual batch number before use. UKAD does not endorse specific products, but Informed Sport is the batch-tested programme its guidance points athletes towards. It will not eliminate every contamination risk — Świątek’s case shows that risk can sit outside the supplement aisle entirely — but in the categories where you do have a choice, it is the single best one available.

You can browse all Informed Sport products on Certwell, or read the longer reference on how Informed Sport testing works.