Sports supplements cover several categories that differ enormously in both evidence and risk. Grouping them together is the main reason people end up taking things that do nothing alongside things that do quite a lot.
- Protein powders. Food in concentrated form. Effects are mostly digestive. See protein powder side effects.
- Creatine. Among the best-evidenced supplements available. Effects are mild, mostly water retention and digestive. See creatine side effects.
- Pre-workouts. Stimulant products, where most of the real risk sits. See pre-workout side effects.
- Amino acid products such as BCAAs. Generally well tolerated, with limited benefit for anyone already eating adequate protein. See BCAA side effects.
- Testosterone boosters and muscle-building products. The category with the highest rate of undeclared ingredients. See testosterone booster side effects.
Common side effects reported with this supplement or ingredient
- Bloating, wind and digestive discomfort, most with protein powders and creatine
- Palpitations, anxiety and insomnia from stimulant products
- Water retention with creatine
- Acne, reported with several product types
- Headache and dehydration if fluid intake does not keep up
Possible interactions with medicines, chronic conditions or pregnancy
Stimulant-containing products interact with decongestants, ADHD medicines, asthma relievers, thyroid medicine and blood pressure treatment. Creatine and high protein intake both warrant care with existing kidney disease.
Several products in this category have been associated with liver injury, so mention them if liver tests come back raised. See supplements causing liver problems.
Who should speak to a healthcare professional before using it?
Anyone with kidney disease, liver disease, a heart condition, high blood pressure or a thyroid condition, and anyone under 18, for whom most of these products are not appropriate.
Also anyone taking a stack of several products at once, which is where interactions and duplicated stimulants accumulate.
Dose, product-quality and stacking risks
Contamination and undeclared ingredients are the specific risk in this category. Sports products have been found internationally to contain substances not listed on the label, including stimulants and, in muscle-building products, anabolic agents. Two consequences follow.
- If you are drug tested for sport or work, a supplement is a genuine route to a positive result, and responsibility usually sits with the athlete regardless of intent.
- Health risk you cannot screen for. A pharmacist cannot warn you about an ingredient the label does not mention.
Buy from reputable retailers, look for third-party testing where it matters to you, and treat dramatic performance claims as a warning rather than a selling point. See unsafe supplements in South Africa.
Stacking is normal in this category and is where problems arise. A pre-workout, an energy drink and a fat burner can deliver several times the caffeine anyone intended. Add up the stimulant content across everything you take on a training day.
When to stop and get medical advice
Get emergency help for chest pain, fainting, a sustained racing or irregular heartbeat, collapse, or severe headache.
Stop and seek advice for yellowing of the eyes or skin, dark urine, persistent nausea or unusual tiredness; passing much less urine than usual; or severe muscle pain with very dark urine after training, which needs urgent assessment.
Related supplement safety guides
- Supplement side effects
- Unsafe supplements in South Africa
- Supplement and medicine interactions
- When to see a doctor about a supplement
- Report a supplement side effect
See also gym supplement side effects.
Medical Disclaimer: This content is for informational and educational purposes only and does not constitute medical diagnosis, prescription, or professional advice. Always read the patient information leaflet and consult a qualified doctor or pharmacist regarding any medicine or health concern.