Everyone has zinc in their bodies. It’s not much, about 1/8 of a teaspoon. Still, it is vital to immune system function, tissue growth, carbohydrate use, vitamin A metabolism, the sense of smell, the sense of taste, and the activity of over a hundred critical enzymes. As a nutrient, zinc is an essential mineral that all of us must have in our diet. However, as with any good thing, too much zinc is bad. While there are several ways to get too much zinc, this article will focus on ingesting too much. Overdosing on zinc can happen slowly and steadily over a long period or all at once. Either way, too much zinc makes people sick. The first symptoms often involve the digestive system: diarrhea, abdominal pain, nausea, vomiting, and possible blood in the vomit. Zinc can be caustic and may burn the gastrointestinal tract, so it doesn’t take long to start feeling bad after ingesting too much of it. People who overdo zinc steadily over time may have gastrointestinal complaints but will also gradually develop chronic symptoms of anemia, weakened immune system, and nerve damage.
Too much zinc (chronic zinc toxicity) is a health condition that can affect anyone regardless of age, sex, race, or ethnicity. Acute zinc toxicity is a rare medical condition.
Early signs of too much zinc include diarrhea, abdominal pain, nausea, vomiting, appetite loss, and possible blood in the vomit.
Any acute symptom of too much zinc requires immediate medical attention, particularly watery diarrhea or bloody vomit.
Too much zinc is caused by taking too many dietary supplements or zinc-containing cold medications, overusing denture cream, eating objects made of zinc (like pennies), ingesting industrial chemicals, improper intravenous feeding, or breathing in zinc fumes. You may be at risk for developing too much zinc symptoms if you regularly take zinc-containing supplements, use denture cream, or have PICA (an eating disorder primarily affecting children, where patients eat inedible objects).
Too much zinc requires a medical diagnosis.
Acute zinc poisoning generally requires treatment. Too much zinc symptoms typically resolve in a few days by removing exposure to zinc, but complications may take longer to resolve.
Treatment of too much zinc may include eliminating excess zinc from the diet, supportive care, antinausea drugs, drugs that remove zinc from the blood (called chelating agents), or whole bowel irrigation or surgery if solid objects have been ingested.
Untreated too much zinc could result in complications like gastrointestinal bleeding, dehydration, copper deficiency, anemia, impaired immune function, slow wound healing, high cholesterol, hair loss, kidney injury, or liver injury.
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Consuming excessive amounts of zinc (200 to 800 mg in a day) will cause gastrointestinal symptoms within three to 10 hours, and so the early signs of too much zinc could be:
Diarrhea
Diffuse abdominal pain
Nausea
Vomiting
Bloody vomiting
Loss of appetite
Regularly ingesting more than the daily upper limit of zinc (40 mg per day) may not have an effect for months or years, until blood counts are low enough or nerve damage is bad enough, a medical condition called “swayback.” The early signs of chronic zinc overdosing may be tiredness, weakness, lightheadedness, numbness, tingling, or loss of coordination. However, according to one study, about half of people taking doses of around 150 mg per day have gastrointestinal symptoms first.
Zinc poisoning symptoms depend on whether a large overdose of zinc has been consumed in a short period (acute zinc toxicity) or a bit too much zinc is ingested over an extended period (chronic zinc toxicity).
The early symptoms of acute zinc poisoning are:
Diarrhea
Watery diarrhea
Abdominal pain
Loss of appetite
Nausea
Vomiting
Bloody vomiting
When extremely high doses of zinc are absorbed into the body, symptoms can include:
Lethargy
Dizziness
High but not excessive zinc intake over a period will cause low levels of copper, an essential micronutrient. This, in turn, causes anemia, bone marrow suppression, and nerve damage. The upper limit of daily zinc intake is 40 mg. Ingesting even 50 mg of zinc per day ymay eventually cause anemia. Symptoms of chronic zinc toxicity include:
Tiredness
Low energy
Lethargy
Dizziness
Lightheadedness
Tingling or numbness
Muscle weakness
Irritability
Mild depression
Poor coordination
Walking abnormalities
Confusion
Susceptibility to infections
Susceptibility to fractures
It’s also possible for people to get zinc poisoning by breathing in too much zinc. The people most at risk are industrial workers exposed to metal fumes, most commonly in welding or smelting facilities. Called metal fume fever (MFF), flu-like symptoms appear within a few hours of exposure. These include fever, cough, trouble breathing, chest pain, fatigue, and muscle weakness. Metal fume fever is not life-threatening, and symptoms typically resolve without treatment in a few days, when the person is removed from the metallic fumes.
The symptoms of zinc overdose and irritable bowel syndrome can be very similar, but there are crucial differences. Irritable bowel syndrome (IBS) is due to a functional disconnect between the brain and the intestines. The result is an overactive digestive system, one that works too hard to pass stuff through. Zinc, on the other hand, is caustic. It can burn and corrode tissues. Unlike IBS, too much zinc can cause vomiting and gastrointestinal bleeding. People can even vomit up blood. The abdominal pain is more diffuse with too much zinc. Above all, IBS comes and goes. Zinc toxicity only happens when people ingest too much zinc.
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Healthcare providers distinguish between three types of zinc poisoning:
Acute zinc toxicity is a rare medical condition resulting from eating large amounts of zinc in a day or a few days. The most common symptoms are gastrointestinal problems like watery diarrhea, vomiting, blood in the vomit, and loss of appetite. Acute zinc toxicity is more likely to happen to children who ingest zinc supplements or eat pennies, but some adults have overdosed on supplements.
Chronic zinc toxicity results from taking too much zinc over a long period, which may not be a large enough dose to cause acute gastrointestinal symptoms. Over time, excess zinc ingestion results in copper deficiency, which can cause nerve damage, nerve dysfunction, and anemia. Chronic zinc toxicity is more common than the acute version. It’s most commonly the result of overdoing zinc or zinc-containing supplements, but people who do not use denture cream as instructed can also develop the problem.
Metal fume fever results from breathing too much zinc particulates, most commonly in an industrial setting. Symptoms are similar to the flu and resolve in a few days if exposure to metal fumes is stopped.
See a doctor if experiencing any symptoms of zinc poisoning, especially if you’ve been overdoing zinc supplements. Go to an emergency room or call a poison helpline if experiencing symptoms of acute zinc toxicity, particularly severe watery diarrhea or vomiting up blood. Bring along any zinc supplements or zinc lozenges that are being taken.
Healthcare providers diagnose zinc toxicity based on the symptoms and a detailed medical history. Whether the problem is chronic or acute, the clinician will test the blood for zinc, copper levels, and ceruloplasmin, a protein that carries copper around the bloodstream. The clinician will also ask for a blood test measuring liver and kidney function. If there’s any suspicion that the person has swallowed solid objects like pennies, an abdomen X-ray will be needed.
The complications of too much zinc include:
Dehydration (due to diarrhea or vomiting)
Gastrointestinal bleeding
Elevated risk of prostate cancer (extremely high doses or long-term overuse)
Slow wound healing
High cholesterol with low HDL (high-density lipoprotein or “good” cholesterol)
Hair loss
Liver injury (acute zinc poisoning)
Kidney injury
In many cases, both chronic and acute zinc poisoning are treated by stopping zinc supplements or other sources of zinc exposure. The primary goal of treatment is to prevent complications. To prevent dehydration, acute zinc poisoning may require drinking fluids and antiemetics, drugs that relieve nausea and vomiting. If a child or other person has ingested solid objects like pennies, an upper endoscopy will likely be needed to retrieve the object, however whole bowel irrigation or surgery may be necessary if the object has made it past the stomach and down into the intestines. Finally, in cases involving neurological symptoms of zinc toxicity, healthcare professionals may use chelating agents that remove zinc from the bloodstream.
Acute zinc poisoning is rare. When it does happen, symptoms usually improve in a few days after the person stops ingesting zinc. The same applies to metal fume fever. People usually feel better just by going home for a few days (if the exposure is at work). Chronic zinc poisoning is more common than acute zinc toxicity. Stopping the zinc will allow the body to absorb copper normally, so copper levels should return to normal. Anemia, low white blood cells, and neurological problems may take longer to improve. Some complications may be long-term problems.
According to the NIH, the recommended daily allowance of zinc is 9 milligrams (mg) per day for adult women, 11 mg per day for men and pregnant women, and 12 mg per day for breastfeeding women. The tolerable upper intake level is 40 mg daily. Supplemental zinc has health benefits for people with zinc deficiency, but be aware of all the zinc you take daily. This includes various forms of zinc, such as zinc supplements, multivitamins, common cold medications, denture creams, and food sources like red meat. A half-pound burger or one Zicam Cold Remedy tablet has enough zinc to meet all an adult’s RDA of zinc. Enriched breakfast cereal is also high in zinc. Denture adhesive cream is a major source of chronic zinc toxicity. All it takes is to go through one 2.4-ounce tube every week to produce symptoms of too much zinc in a few years. If you’re unsure whether your zinc intake is too low or too high, get medical advice from a healthcare professional.
The effects of zinc on the human body, including on renal failure and renal transplantation, Journal of Medicine and Life
The essential toxin: impact of zinc on human health, International Journal of Environmental Research and Public Health
Zinc: health professionals fact sheet, NIH Office of Dietary Supplements
Zinc, LiverTox
Zinc toxicity, StatPearls
Zinc toxicity, Merck Manual Professional Version
Zinc toxicity, StatPearls
The effect of zinc supplements on plasma zinc levels and the reported symptoms in healthy volunteers, MJA
Anemia treatments and medications, SingleCare
IBS treatments and medications, SingleCare
What causes high calcium? Diagnosis, prevention, and treatment, SingleCare
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