Zinc is widely taken for immune support, skin and general wellbeing. Short courses at ordinary amounts are usually well tolerated. The effects worth knowing about come from taking it on an empty stomach, and from taking higher amounts for a long time.
Common side effects reported with this supplement or ingredient
- Nausea, which is the most common complaint and is much more likely on an empty stomach
- A metallic taste in the mouth
- Stomach discomfort or cramping
- Vomiting or diarrhoea at higher amounts
- Headache
Taking zinc with food usually resolves the nausea, though food also reduces absorption somewhat. A pharmacist can advise on the trade-off for your situation.
Prolonged high intake causes a distinct problem: zinc and copper compete for absorption, so sustained high zinc can lead to copper deficiency. That can present as anaemia that does not respond to iron, unusual tiredness, or numbness and weakness in the limbs. It develops over months rather than days, and is a reason not to take high-dose zinc indefinitely without advice. See too much zinc symptoms.
Possible interactions with medicines, chronic conditions or pregnancy
- Some antibiotics, including tetracyclines and quinolones, whose absorption zinc reduces. Separate by a few hours.
- Iron and calcium supplements, which compete with zinc for absorption in both directions
- Penicillamine and some other medicines whose effect zinc reduces
- Diuretics, which can increase zinc loss
- Pregnancy and breastfeeding. Zinc is included in many prenatal products at set amounts; check before adding more.
Who should speak to a healthcare professional before using it?
Ask first if you have a copper metabolism disorder, kidney disease, a condition affecting absorption from the gut, or if you plan to take zinc at high strength for longer than a short course. If you are taking zinc for recurrent infections or persistent skin problems, those warrant a proper assessment rather than an indefinite supplement.
Dose, product-quality and stacking risks
Supplements in South Africa are regulated as complementary medicines, and the checks applied are not the same as those for prescription medicines. Strength, purity and labelling can vary between products. See how supplements are regulated in South Africa and how to check supplement labels.
Stacking is a common problem: several products each containing the same ingredient add up to more than intended. Read the ingredients on everything you take. See taking too many supplements.
Zinc is in multivitamins, immune-support formulas, cold remedies, lozenges and men’s health products. Taking two or three of these together is the usual route to an unintentionally high daily total. Different zinc salts also deliver different amounts of elemental zinc for the same label figure.
When to stop and get medical advice
Stop and seek advice for persistent vomiting or diarrhoea, unexplained and worsening tiredness, numbness or weakness in the hands or feet, or repeated infections while taking high-dose zinc long term. Take the product with you so the actual amount can be checked.
Related supplement safety guides
- Supplement side effects
- Supplement and medicine interactions
- When to see a doctor about a supplement
- Unsafe supplements in South Africa
- Report a supplement side effect in South Africa
See also vitamin and mineral 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.