Merck Manual

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Laura Shane-McWhorter

, PharmD, University of Utah College of Pharmacy

Last full review/revision Jul 2020| Content last modified Jul 2020
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Medicinal claims

People most often take zinc in the form of lozenges to reduce the duration of cold symptoms. Scientific studies are inconsistent, but if zinc has an effect, it probably is small and occurs only when it is taken very soon after cold symptoms develop.

Some people take zinc to slow the progression of age-related macular degeneration Age-Related Macular Degeneration (AMD or ARMD) Age-related macular degeneration (AMD) causes progressive damage to the macula, the central and most vital area of the retina, resulting in gradual loss of central vision. Central vision becomes... read more Age-Related Macular Degeneration (AMD or ARMD) , which is an eye disease, or to help heal wounds because zinc deficiency delays wound healing. In developing countries, once weekly supplements containing zinc and iron during the first year of life may decrease mortality due to diarrhea and respiratory infections. In children older than 6 months who are undernourished or who have a zinc deficiency, zinc supplementation may help treat diarrhea.

Zinc may also help decrease blood glucose levels in people with diabetes or pre-diabetes.

Mild zinc deficiency impairs growth in children and can be corrected with zinc supplementation.

Possible side effects

Zinc is generally safe, but toxicity can develop if high doses are taken. The common side effects of zinc lozenges include the following:

  • Nausea

  • Vomiting

  • Diarrhea

  • Mouth irritation

  • Mouth sores

  • Bad taste

Because zinc is a trace metal and can remove other necessary metals from the body, intake of zinc lozenges should be limited (for example, to no more than 14 days). Zinc sprays may irritate the nose and throat.

Possible drug interactions

The absorption and effectiveness of certain antibiotics in treating infection may be lowered if zinc supplements are taken at the same time; therefore, zinc should be taken at least 3 hours after these antibiotics.

More Information about Zinc

The following is an English-language resource that may be useful. Please note that THE MANUAL is not responsible for the content of this resource.

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Ayurveda is the traditional medical system of India. Its practices are distinctly different from those used in Western medicine. Which of the following is NOT typically used in Ayurvedic treatment? 
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