Zinc

Is zinc safe?

Updated 10 Nov 2026

Short answer

At or below the upper limit, zinc is unlikely to cause harm. The US sets this limit at 40 mg a day for adults, and the EU at 25 mg.[1][2]

Too much zinc can cause nausea, dizziness, headaches, stomach upset, vomiting and loss of appetite.[1] Doses of 50 mg or more for weeks can lower copper absorption, weaken immune function and lower HDL cholesterol.[1] In a 2012 review of cold trials, zinc taken by mouth caused more bad taste and nausea than placebo.[3]

Zinc can interact with quinolone and tetracycline antibiotics and with penicillamine. Thiazide diuretics raise the loss of zinc in urine.[1] Ask a doctor or pharmacist first if you take one of these medicines or plan to take more than the upper limit.[1]

Sources (3)

  1. Zinc: Fact Sheet for Health Professionals. NIH Office of Dietary Supplements. ods.od.nih.gov
  2. Overview on Tolerable Upper Intake Levels as derived by the Scientific Committee on Food (SCF) and the EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA). European Food Safety Authority (EFSA), 2025. www.efsa.europa.eu
  3. Zinc for the treatment of the common cold: a systematic review and meta-analysis of randomized controlled trials. Science M, Johnstone J, Roth DE, Guyatt G, Loeb M CMAJ, 2012. PMID 22566526

More about zinc

What is zinc?Which foods contain zinc?What is zinc used for?What are the signs of zinc deficiency?Do zinc lozenges help with colds?Does zinc help children with diarrhea?

For education; not medical advice. Talk to a doctor before you start, stop or change a supplement.