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Ingredient guide

Zinc side effects: what too much can do

Written by the Full Measure editorial team, which sells supplements. Approved for publication by the Full Measure owners. Updated .

Drafted with AI assistance from the sources listed below. How we write these

Quick answer

Within the 40 mg adult upper limit, zinc from all sources is unlikely to cause harm. Above it, nausea, vomiting, loss of appetite, stomach cramps and headaches are the usual complaints. Taken for weeks, 50 mg a day or more can also lower the body's copper and weaken immune function.1,2

Key facts

  • The upper limit is 40 mg a day for adults and 7 mg for children aged 1 to 3.1
  • About 60 mg of zinc a day for up to 10 weeks lowered a marker of copper status.3
  • Almost all multivitamins contain zinc, so amounts from several products can add up.2
  • Thiazide diuretics raise the amount of zinc lost in urine.2

Common side effects

Too much zinc can cause nausea, vomiting, loss of appetite, stomach cramps, diarrhea and headaches. Dizziness has also been reported.1,2,4

High intakes can leave a metallic taste in the mouth.4

The upper limit for adults is 40 mg of zinc a day from all sources: food, drinks, supplements and medicines, including during pregnancy and breastfeeding. It is 34 mg for teens aged 14 to 18 and lower for children. It is set to protect copper status and does not apply to people given zinc as medical treatment by a doctor.1,2

Copper: the long-term risk

Taking 50 mg of zinc a day or more for weeks can block copper absorption and lower copper status, reduce immune function and lower HDL cholesterol.1,2

Low copper is why the upper limit sits at 40 mg. NIH puts the risk at 50 mg a day or more taken for weeks, and one marker of copper status fell with about 60 mg a day.1,3

Using far more zinc-containing denture cream than directed, at least a 70 g tube a week for several years, has led to low copper with numbness, weakness and loss of coordination.1,2

Children

Zinc upper limits for children, from all sources1
AgeUpper limit per day
Birth to 6 months4 mg
7 to 12 months5 mg
1 to 3 years7 mg
4 to 8 years12 mg
9 to 13 years23 mg
14 to 18 years34 mg

Children's limits are much lower than the adult 40 mg, so ask a doctor before giving a child a zinc supplement.1

Very high doses

Very high doses from supplements, about 142 mg of zinc a day, might interfere with magnesium absorption.1

Food rarely supplies as much as 50 mg of zinc a day, so zinc from food alone is unlikely to cause too much.1

Zinc in medicines and denture creams counts toward the limit as well as zinc in food and supplements.2

Medicines and zinc

Your doctor may want to check on you

Thiazide diuretics such as hydrochlorothiazide and chlorthalidone increase the zinc lost in urine, and taking them for a long time might lower the body's zinc.1,2

Reported in studies

Zinc can also keep quinolone and tetracycline antibiotics, and penicillamine, from being absorbed properly. The page on zinc and antibiotics sets out what NIH and the labels say.2

Men and women

The 40 mg limit is the same for men and women, including in pregnancy. Men need 11 mg a day and women 8 mg, so the margin between need and limit is wide for both.1

Questions people ask

Is it OK to take zinc every day?

NIH defines the 40 mg adult upper limit as the most you can take each day without likely harm, counting food, drinks, supplements and medicines. Long-term doses of 50 mg a day or more can lower copper.1,2

Why does zinc upset my stomach?

Nausea is one of the most common effects of too much zinc, along with vomiting and stomach cramps. Check the total from every product you take against the 40 mg limit, and ask a pharmacist if it continues.1,2

Can zinc cause a copper deficiency?

Yes, at high doses over time. Zinc blocks copper absorption in the gut, and people who overused zinc denture creams for years developed numbness and weakness from low copper.1,3

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Sources

  1. National Institutes of Health, Office of Dietary Supplements. Zinc: Fact Sheet for Health Professionals. Updated January 6, 2026. Opened 2026-10-07.
  2. Office of Dietary Supplements, National Institutes of Health. Zinc: Fact Sheet for Consumers. Updated October 4, 2022. Opened 2026-10-07.
  3. National Institutes of Health, Office of Dietary Supplements. Copper: Fact Sheet for Health Professionals. Updated October 18, 2022. Opened 2026-10-07.
  4. National Institutes of Health, Office of Dietary Supplements. Dietary Supplements for Immune Function and Infectious Diseases: Fact Sheet for Health Professionals. Updated March 10, 2025. Opened 2026-10-07.

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.