Safety and side effects

Oral zinc can cause:

• Indigestion
• Diarrhea
• Headache
• Nausea
• Vomiting

When oral zinc is taken long term and in high doses it can cause copper deficiency. People with low copper levels might experience neurological issues, such as numbness and weakness in the arms and legs.

The National Institutes of Health considers 40 mg of zinc a day to be the upper limit dose for adults and 4 mg of zinc a day for infants under age 6 months.

Don't use intranasal zinc. This form of zinc has been linked with the loss of the sense of smell.