Prohibited substances in supplements: how athletes can avoid an inadvertent positive test
Many athletes who test positive never intended to dope – the prohibited substance came from a supplement. Our editorial team explains strict liability, how contamination happens and how batch testing and careful checks reduce the risk.
Strict liability: why "I didn't know" is not a defence
Under the World Anti-Doping Code, which UK Anti-Doping (UKAD) applies in Britain, athletes are subject to the principle of strict liability. If a prohibited substance or its metabolite is found in a sample, an anti-doping rule violation has occurred regardless of intent. Lack of knowledge may reduce a sanction, but it does not prevent one.
This matters because many positive tests in recent decades have been traced not to deliberate doping but to supplements. An athlete buys a pre-workout, fat burner or "test booster" in good faith, and the product turns out to contain a stimulant, an anabolic agent or a diuretic that was not on the label – or was listed under an unfamiliar name.
Strict liability applies to everyone in the testing pool, including amateur and masters athletes in many sports, university competitors and players in professional leagues. Gym members who enter powerlifting or bodybuilding competitions run under tested federations can also be tested.
The responsibility for checking what you consume therefore rests with you. The purpose of this article is to explain where the risks lie and what practical steps reduce them – not to suggest any way of influencing the result of a legitimate test.
How contamination happens
Supplements in the UK are regulated as foods. They do not require pre-market approval or proof of efficacy, and manufacturers are responsible for ensuring safety and accurate labelling. Enforcement is carried out by local trading standards and the Food Standards Agency, but the system cannot test every batch on the market.
An international study by Geyer and colleagues, published in 2004, analysed over 600 non-hormonal supplements bought in 13 countries and found that around 15% contained anabolic-androgenic steroids not declared on the label. Products from the UK were among those affected. Later reviews, including Martínez-Sanz and co-workers in 2017, confirmed that contamination remains a recurring problem.
- Cross-contamination: the same production line is used for a hormone product and then for an ordinary supplement without adequate cleaning.
- Deliberate adulteration: a stimulant or anabolic agent is added to make a product "work" and generate repeat sales.
- Misleading names: a prohibited substance is listed under a botanical or chemical synonym that few athletes would recognise.
- Contaminated raw materials: an ingredient bought from a third party already contains traces of a prohibited compound.
Even very small amounts can lead to an adverse analytical finding, because modern laboratory methods detect substances at extremely low concentrations. A contaminant at a level that has no physiological effect can still be reported.
Which product categories carry the greatest risk
Not all supplements carry the same risk. Single-ingredient products such as creatine monohydrate, whey protein or vitamin D from reputable manufacturers are generally lower risk, although not risk-free. Multi-ingredient products marketed for rapid results are a different matter.
| Category | Typical prohibited substances found | Risk level |
|---|---|---|
| Testosterone or "anabolic" boosters | Prohormones, anabolic steroids, SARMs | High |
| Fat burners and weight-loss products | Stimulants (e.g. DMAA, sibutramine), diuretics | High |
| Pre-workout formulas | Stimulants such as DMAA, DMBA, higenamine | High |
| Protein and gainers | Occasional cross-contamination | Moderate–low |
| Single vitamins and minerals | Rare | Low |
Products bought from unfamiliar websites, foreign marketplaces and social-media sellers carry additional risk, because their manufacturing standards cannot be verified. Cohen and colleagues found that many supplements recalled by the US Food and Drug Administration were still on sale months later and still contained banned drugs.
Practical steps to reduce the risk
The International Olympic Committee consensus statement on dietary supplements, published in 2018, advises athletes to undertake a cost–benefit analysis before using any supplement. The first question should always be whether the product is needed at all.
If a supplement is justified, choose a product that has been batch-tested under a recognised third-party programme. In the UK the most widely used scheme is Informed Sport, which tests every batch before release; Informed Choice offers a related monthly testing approach. Other schemes exist internationally. Testing reduces risk but cannot eliminate it completely.
Check individual ingredients against the Global DRO database, which UKAD supports for checking the status of medicines. Keep a record of each product, including batch number and receipt, and retain a sealed sample where possible – this can be vital evidence if a case arises.
Medicines also deserve attention. Some cold and flu remedies, asthma inhalers and prescription drugs contain prohibited substances. If you need a medicine that is prohibited, a Therapeutic Use Exemption may be required, and your doctor should be told that you are subject to anti-doping rules.
Editorial team's conclusions
Inadvertent doping through supplements is a real and well-documented risk. Because of strict liability, an athlete can be sanctioned for a substance they never knowingly took.
The safest approach is a "food first" strategy, minimal supplement use, preference for batch-tested products, and careful checking of medicines. Multi-ingredient boosters, fat burners and pre-workouts deserve particular caution.
Documentation – receipts, batch numbers and retained samples – costs little and may matter greatly. Ask your sport's governing body or UKAD's advice line if in doubt.
Related reading on our site includes articles on Therapeutic Use Exemptions, on how to read a supplement label, and on stimulants in pre-workout formulas.
References
- Geyer H, Parr MK, Mareck U, et al. Analysis of non-hormonal nutritional supplements for anabolic-androgenic steroids – results of an international study. Int J Sports Med. 2004;25(2):124–129.
- Martínez-Sanz JM, Sospedra I, Ortiz CM, et al. Intended or unintended doping? A review of the presence of doping substances in dietary supplements used in sports. Nutrients. 2017;9(10):1093.
- Maughan RJ, Burke LM, Dvorak J, et al. IOC consensus statement: dietary supplements and the high-performance athlete. Br J Sports Med. 2018;52(7):439–455.
- Outram S, Stewart B. Doping through supplement use: a review of the available empirical data. Int J Sport Nutr Exerc Metab. 2015;25(1):54–59.
- Cohen PA, Maller G, DeSouza R, Neal-Kababick J. Presence of banned drugs in dietary supplements following FDA recalls. JAMA. 2014;312(16):1691–1693.
- World Anti-Doping Agency. World Anti-Doping Code 2021. Montreal: WADA; 2021.
