Why athletes fail drug tests they never meant to take

What happens when an athlete is tested

The call usually comes without warning. Chaperones from anti-doping agencies can turn up at an athlete's training ground, their home, or immediately after a race. They must keep the athlete in sight at all times until a sample is collected.

Athletes provide urine, blood, or both. The samples are split into an 'A' bottle and a 'B' bottle. The laboratory analyses the A sample first; the B sample is kept in reserve, sealed and frozen, to be opened only if the first sample returns an adverse analytical finding.

Over the longer term, sports bodies track an athlete's biological passport. This does not look for specific drugs, but rather monitors the body's variables — like red blood cell counts — over time. Sudden spikes or drops signal that something is amiss, even if the substance itself has cleared the system.

The trap of contamination

Many failed tests do not start with a syringe. They start with a meal, a cosmetic, or a contaminated over-the-counter supplement.

Because the supplement industry is loosely regulated, some products contain ingredients not listed on the label. A protein powder blended in a factory that also handles banned stimulants can lead to a positive test.

Food is another hazard. In some parts of the world, livestock are treated with clenbuterol, a steroid that builds lean muscle. Athletes eating local beef have tested positive as a result. Others have blamed contaminated medication, skin creams, or even intimate contact with a partner who was taking a prescription drug.

But proving these claims to an independent panel is notoriously difficult.

The strict liability rule

Under the World Anti-Doping Code, the governing principle is "strict liability". This means that an athlete is responsible for any prohibited substance found in their specimen, regardless of how it got there or whether there was any intent to cheat.

If a banned substance is in your system, you have committed an anti-doping rule violation.

The burden of proof then shifts entirely to the athlete. To avoid a multi-year ban, they must prove how the substance entered their body and demonstrate that they bore "no significant fault or negligence".

Gathering this evidence can take months and cost tens of thousands of pounds in legal and scientific fees. Athletes must sometimes buy and test packets of the same supplement batch, or track down receipts from a restaurant to prove they ate a certain meat. Even then, sports tribunals frequently rule that the athlete should have been more careful.

The paperwork loophole

For athletes with legitimate medical conditions, there is a system called a Therapeutic Use Exemption (TUE). This allows them to take banned substances — such as insulin for diabetes, or ADHD medication — under strict medical supervision.

To get a TUE, an athlete’s doctor must submit detailed medical records proving that the athlete would suffer significant health problems without the drug, and that the substance will not provide a performance boost beyond returning them to normal health.

The process is bureaucratic and unforgiving. A single missed deadline, a clerical error by a doctor, or a failure to renew an exemption before it expires can turn a legitimate medical treatment into a doping violation. In the eyes of the regulators, a paperwork error is treated with the same initial severity as deliberate cheating.