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Last updated: Oct 27, 2021
6 min read

Signs and symptoms of zinc overdose

felix gussone

Medically Reviewed by Felix Gussone, MD

Written by Health Guide Team

Disclaimer

If you have any medical questions or concerns, please talk to your healthcare provider. The articles on Health Guide are underpinned by peer-reviewed research and information drawn from medical societies and governmental agencies. However, they are not a substitute for professional medical advice, diagnosis, or treatment.

Your body needs zinc in order to work properly. The essential mineral is found mostly in your bones and muscles, but it’s also in your brain, skin, stomach, and other organs. It’s critical for early development, cell health, and the health of your immune system (Gupta, 2020). But a zinc overdose may occur if you swallow too much of the stuff—for example, in the form of supplements.  

A zinc overdose—also known as zinc toxicity or zinc poisoning—can cause many different symptoms. Fortunately, zinc appears to be relatively safe, and serious life-threatening overdoses are uncommon when it comes to the zinc found in food and supplements such as multivitamins (Gummin, 2018). 

That said, overdoing it with supplements may raise your risks for some longer-term health complications (Bartzatt, 2017). Let’s look at how a zinc overdose happens and what signs and symptoms to watch out for.

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Can you overdose on zinc?

Almost anything you eat contains at least some amount of zinc. But animal products (red meat and dairy), as well as oysters and shellfish, are the best ways for your body to get zinc from food (Gupta, 2020).

Zinc is also available as a dietary supplement, including zinc lozenges. It’s an ingredient in denture creams, and it’s also found in some types of sunscreen, makeup, ointments, and other products that you apply to your skin (Agnew, 2021).  

Most of the time, even with the above daily consumption and exposure to zinc, you will likely stay within its recommended daily intake (RDA). That said, it is possible to overdose on zinc. If an overdose does occur, it’s due to one of the three ways people get excess zinc into their bodies. These are through ingestion, inhalation, and absorption through the skin (Bartzatt, 2017).

Ingestion

When it comes to dietary zinc, the recommended daily intake (RDA) is between 2 mg and 13 mg, depending on a person’s age and other factors (IOM, 2001). Some research has found that you’d have to swallow 1,000 mg or 2,000 mg of zinc—or approximately 100x the RDA—before acute symptoms of an overdose would show up (Agnew, 2021). 

There’s not much evidence that people overdose on zinc from food sources. But if you take supplements that contain high doses of zinc, it’s possible that you could ingest too much of the mineral.

There is some documentation of cases where someone swallows a large amount of over-the-counter nutritional supplements and develops a zinc overdose (Agnew, 2021). There’s also evidence that taking too much zinc in supplement form could lead to some longer-term health problems (Bartzatt, 2017). 

Denture adhesive creams can also contain zinc. If you use too much of these adhesive creams, you may swallow some of the cream, which could mean you’re ingesting more zinc than you need (Agnew, 2021).

Inhalation and absorption

When it comes to inhalation, industrial processes can expose your lungs to zinc. For example, the process of treating metals with zinc to prevent rust—sometimes known as galvanization—can cause a dangerous zinc overdose (Bartzatt, 2017). So can some types of welding or other metalwork (Agnew, 2021).

Finally, it may be possible to overdose on zinc through skin absorption of sunscreens, makeup, or other substances that contain zinc oxide. But this seems to be very uncommon (Bartzatt, 2017).

How much zinc is too much?

When it comes to nausea, stomach pain, and other short-term intestinal symptoms, it seems like you need to swallow a lot of zinc—at least 1,000 mg—before these symptoms will emerge (Agnew, 2021).

But when it comes to some of the longer-term issues or complications associated with zinc, the picture gets murkier. Some medical research shows that there is no association between problem side-effects and taking 440 mg of zinc daily for several months (Santos, 2020). But older studies show that taking such heavy doses may eventually lead to copper deficiencies, blood imbalances, and other health problems (Nriagu, 2011). 

Meanwhile, research on people who have zinc deficiencies shows that taking 2–3 mg of zinc per kilogram of body weight is enough to resolve most or all health-related concerns. That works out to between 68 and 136 mg of zinc per day for a 150-pound person—far below the levels that some other work links to risks (Maxfield, 2021).  

While serious zinc overdoses from foods or supplements seem to be uncommon, many people are walking around with a zinc deficiency. Some experts estimate that roughly 80% of women are low in zinc (Bostanci, 2015). People who eat a primarily plant-based diet may be at higher risk for low zinc as well (Gregory, 2017). The same is true for women who are pregnant or nursing (Bostanci, 2015).

Zinc overdose symptoms

If you swallow too much zinc, the first symptoms you may experience are gastrointestinal side-effects such as nausea, vomiting, and abdominal pain. Diarrhea and muscle cramps are also possible. As time passes, you may experience sleepiness, dizziness, or fatigue (Bartzatt, 2017; Agnew, 2021).

If you inhale zinc, this can cause several short-term symptoms. These are (Bartzatt, 2017):

  • Fatigue
  • Nausea
  • Fever
  • Chest pain
  • Cough
  • Problems breathing
  • Muscle soreness

Again, industrial exposures usually cause these sorts of inhalation-related zinc issues (Bartzatt, 2017). Zinc overdose is rarely fatal whether you’re exposed to zinc in foods, supplements, or elsewhere (Agnew, 2021).

Complications of overdosing on zinc

Overdoing it on zinc can lead to low red blood cell counts (anemia) and other blood-related problems in the long term. It can also cause nerve numbness or weakness, problems walking or moving, and muscle spasms. These symptoms may indicate something called “swayback,” a syndrome caused by zinc-related changes in the body’s copper levels (Agnew, 2021).  

There’s also some evidence that overdoing it on zinc supplements could impair the function of your pancreas, and there is research that links high zinc intakes to cholesterol imbalances and possibly issues with the way the brain’s neurons transmit information (Nriagu, 2011).  

How is zinc overdose diagnosed?

Diagnosis is tricky. The symptoms of a zinc overdose overlap with the symptoms of many other much more common medical conditions. Unless you’ve inhaled zinc or experienced some other obvious type of heavy zinc exposure, your medical provider will probably look at other culprits before considering your zinc intake (Agnew, 2021).  

That said, one of the few indicators of a zinc overdose is anemia (low red blood cell counts) that does not respond to other treatments, such as iron supplements. If your healthcare provider suspects that a zinc overdose may be causing your health issues, blood tests can help determine if zinc is to blame (Agnew, 2021). 

To sum this up, zinc seems to be a relatively safe nutrient. You can overdo it, and this can cause both short-term and long-term health problems. But most of these problems are associated with the heavy use of supplements or other non-food exposures. 

If you’re worried that you may be experiencing a zinc overdose, seek medical advice or call your local poison control center. 

References

  1. Agnew, U. M., & Slesinger, T. L. (2021). Zinc Toxicity. [Updated Apr 28, 2021]. In: StatPearls [Internet]. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK554548/ 
  2. Bartzatt, R. (2017). Neurological Impact of Zinc Excess and Deficiency In vivo. European Journal of Nutrition & Food Safety, 7(3), 155-160. doi: 10.9734/EJNFS/2017/35783. Retrieved from https://www.researchgate.net/profile/Ronald-Bartzatt/publication/319200315_Neurological_Impact_of_Zinc_Excess_and_Deficiency_In_vivo/links/599c8eb6aca272dff12bbf11/Neurological-Impact-of-Zinc-Excess-and-Deficiency-In-vivo.pdf
  3. Bostanci, Z., Mack, R. P., Jr, Lee, S., Soybel, D. I., & Kelleher, S. L. (2015). Paradoxical zinc toxicity and oxidative stress in the mammary gland during marginal dietary zinc deficiency. Reproductive Toxicology (Elmsford, N.Y.), 54, 84–92. doi: 10.1016/j.reprotox.2014.07.076. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4312747/
  4. Gregory, P. J, Wahbi, A., Adu-Gyamfi, J., Heiling, M., Gruber, R., Joy, E., et al. (2017). Approaches to reduce zinc and iron deficits in food systems. Global Food Security, 15, 1-10. doi: 10.1016/j.gfs.2017.03.003. Retrieved from https://researchonline.lshtm.ac.uk/id/eprint/4363549/1/Approaches%20to%20reduce%20zinc_GREEN%20AAM.pdf
  5. Gummin, D. D., Mowry, J. B., Spyker, D. A., Brooks, D. E., Osterthaler, K. M., & Banner, W. (2018). 2017 Annual Report of the American Association of Poison Control Centers’ National Poison Data System (NPDS): 35th Annual Report. Clinical Toxicology (Philadelphia, Pa.), 56(12), 1213–1415. doi: 10.1080/15563650.2018.1533727. Retrieved from https://pubmed.ncbi.nlm.nih.gov/30576252/ 
  6. Gupta, S., Brazier, A., & Lowe, N. M. (2020). Zinc deficiency in low- and middle-income countries: prevalence and approaches for mitigation. Journal of Human Nutrition and Dietetics : The Official Journal of the British Dietetic Association, 33(5), 624–643. doi: 10.1111/jhn.12791. Retrieved from https://pubmed.ncbi.nlm.nih.gov/32627912/
  7. Institute of Medicine (US) Panel on Micronutrients (IOM). (2001). Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. National Academies Press (US). doi: 10.17226/10026. Retrieved from https://pubmed.ncbi.nlm.nih.gov/25057538/
  8. Maxfield, L., Shukla, S., & Crane, J. S. (2021). Zinc Deficiency. [Updated Aug 13, 2021]. In: StatPearls [Internet]. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK493231/
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  10. Santos, H. O., & Teixeira, F. J. (2020). Use of medicinal doses of zinc as a safe and efficient coadjutant in the treatment of male hypogonadism. The Aging Male : The Official Journal of the International Society for the Study of the Aging Male, 23(5), 669–678. doi: 10.1080/13685538.2019.1573220. Retrieved from https://pubmed.ncbi.nlm.nih.gov/30767598/