Zinc is an essential mineral involved in over 100 chemical reactions in your body.

It’s necessary for growth, DNA synthesis and taste perception. It also supports wound healing, immune function and reproductive health (1).

Health authorities have set the tolerable upper intake level (UL) for zinc at 40 mg daily for adults. The UL is the highest recommended daily amount of a nutrient. For most people, this amount is unlikely to cause negative side effects (1, 2).

Food sources high in zinc include red meat, poultry, seafood, whole grains and fortified cereals. Oysters contain the highest amount, with up to 673% of the daily value in a 3-ounce serving (1).

Although some foods can provide amounts well above the UL, there are no reported cases of zinc poisoning from naturally occurring zinc in food (2).

However, zinc poisoning can occur from dietary supplements, including multivitamins, or accidental ingestion of zinc-containing household products.

Here are the 7 most common signs and symptoms of zinc overdose.

Nausea and vomiting are common side effects of zinc toxicity.

A 2012 review of 17 studies on the effectiveness of zinc supplements for treating the common cold found that zinc may reduce the duration of a cold, but adverse effects were common. In fact, the review found that study participants receiving zinc had a 64% higher risk of nausea than the control groups. (3).

Although vomiting may help rid the body of toxic amounts of zinc, it may not be enough to prevent further complications.

If you have consumed toxic amounts of zinc, seek medical help immediately.

Summary

Nausea and vomiting are common and often immediate reactions to ingesting toxic amounts of zinc.

Typically, stomach pain and diarrhea occur in conjunction with nausea and vomiting.

In one 2021 review on zinc supplements and the common cold, approximately 40% of participants reported abdominal pain and diarrhea (3).

Although less common, gut irritation and gastrointestinal bleeding can occur.

In one case study, an individual experienced intestinal bleeding after taking 220 mg of zinc sulfate twice daily to treat acne (4).

Zinc chloride is not present in supplements, but poisoning can occur from accidental ingestion of household products. Adhesives, sealants, soldering fluxes, cleaning chemicals and wood finishing products all contain zinc chloride.

Summary

Stomach pain and diarrhea are common symptoms of zinc toxicity. In some cases, severe gastrointestinal damage and bleeding can occur.

Taking more zinc than the established UL may cause flu-like symptoms, such as fever, chills, cough, headache and fatigue (5).

These symptoms occur in many conditions, including other mineral toxicities. Thus, diagnosing zinc toxicity can be difficult.

Your doctor may need your detailed medical and dietary history and blood tests for suspected mineral toxicity.

If you’re taking supplements, be sure to disclose these to your healthcare professional.

Summary

Flu-like symptoms can occur due to toxic amounts of several minerals, including zinc. Thus, it’s important to disclose all supplements to your healthcare provider to ensure proper treatment.

“Good” high-density lipoprotein (HDL) cholesterol lowers your risk of heart disease by clearing cholesterol from your cells, thereby preventing the buildup of artery-clogging plaque.

For adults, health authorities recommend an HDL greater than 40 mg/dL. Lower levels put you at a higher risk of heart disease.

A 2015 meta-analysis found that around 40 mg of zinc a day may lower low-density lipoprotein (LDL) cholesterol by 11.25 mg/dl in non-healthy individuals. Researchers report that zinc supplementation in non-healthy patients can also cause a significant elevation of HDL cholesterol. (6)

While several factors affect cholesterol levels, these findings are something to consider if you take zinc supplements regularly.

Summary

Regular ingestion of zinc above the recommended levels can cause a drop in “good” HDL cholesterol levels, which may put you at a higher risk of heart disease.

Zinc is important for your sense of taste. In fact, zinc deficiency can result in hypogeusia, a dysfunction in your ability to taste (1).

Interestingly, zinc in excess of the recommended levels may also cause taste alterations, including a bad or metallic taste in your mouth.

Typically, this symptom is reported in studies investigating zinc lozenges (cough drops) or liquid supplements for treating the common cold.

While some studies report beneficial results, the doses used are often well above the UL of 40 mg/day, and adverse effects are common (3).

For example, some patients can tolerate zinc doses of up to 100 to 150 mg/day for months with few adverse effects. Therefore, a zinc dose of some 80 mg/day for 1–2 weeks starting at the early symptoms of the common cold is unlikely to cause long-term adverse effects. (7)

If you’re using zinc lozenges or liquid supplements, be aware that these symptoms may continue even during treatment (8).

Summary

Zinc plays a role in taste perception. Excess zinc may cause a metallic taste in your mouth, particularly if taken as a lozenge or liquid supplement.

Zinc and copper compete for absorption in your small intestine.

Doses of zinc above the established UL can interfere with your body’s ability to absorb copper. Over time, this can cause copper deficiency (2).

Copper is an essential mineral. It aids in iron absorption and metabolism, making it necessary for red blood cell formation. It also plays a role in white blood cell formation (9).

Red blood cells transport oxygen through your body, while white blood cells are key to your immune function.

Zinc-induced copper deficiency is associated with several blood disorders (10, 11, 12):

  • Iron deficiency anemia. A lack of healthy red blood cells due to insufficient amounts of iron in your body.
  • Sideroblastic anemia. A lack of healthy red blood cells due to an inability to metabolize iron properly.
  • Neutropenia. A lack of healthy white blood cells due to a disruption in their formation.

Do not mix your copper supplements with zinc if you have a copper deficiency.

Summary

Regular doses of zinc above 40 mg per day can hinder copper absorption. This can result in copper deficiency, which is associated with several blood disorders.

Zinc plays an important role in immune system function, and zinc deficiency can affect its function. However, too much zinc can also suppress your immune response (13, 14).

Zinc toxicity is rare, and immune function impairments normally result from associated anemias and neutropenia, but they can also occur outside of zinc-induced blood disorders.

In test-tube studies, excess zinc reduced the function of T cells, a type of white blood cell. T cells play a central role in your immune response by attaching to and destroying harmful pathogens (15, 16).

Summary

Taking zinc supplements in doses above the UL may suppress your immune response, leaving you more susceptible to illness and infections.

If you believe you may be experiencing zinc poisoning, contact your local poison control center immediately.

Zinc poisoning is potentially life threatening. Therefore, it’s important to seek medical help right away.

If a person ingests large amounts of zinc, surgical removal may be necessary. In other instances, doctors can treat zinc poisoning with calcium disodium edetate or copper sulfate medications.

Calcium disodium edetate helps rid the body of excess zinc by binding to it in the blood. The body then expels it through urine, rather than binding to other cells.

Doctors may also have to treat the physical side effects of zinc poisoning.

For example, doctors will treat zinc poisoning from oral ingestion with antiemetics to stop vomiting and nausea and H2 blockers and proton pump inhibitors (PPIs) to reduce nausea and bile production. Doctors may treat cases of zinc poisoning via inhalation with anti-inflammatory medication to keep airways open (17).

Summary

Zinc poisoning is a potentially life-threatening condition. It’s important to seek medical help immediately.

Although some foods contain zinc well above the UL of 40 mg daily, there are no reported cases of poisoning from naturally occurring zinc.

However, zinc overdose can occur from dietary supplements or accidental excess ingestion.

Zinc toxicity can have both acute and chronic effects. The severity of your symptoms largely depends on the dose and duration of intake.

With acute ingestion of high doses of zinc, gastrointestinal symptoms are likely. In severe cases, such as accidental ingestion of zinc-containing household products, gastrointestinal corrosion and bleeding can occur.

Long-term use may cause less immediate but serious side effects, such as low “good” HDL cholesterol, copper deficiency and a suppressed immune system.

Overall, you should only exceed the established UL under the supervision of a medical professional.