What Happens if Your Selenium Levels Are Too High?

January 1, 2026 •

3 min read

While selenium is a vital trace mineral, consuming too much can be dangerous, leading to a condition called selenosis. Selenosis can cause a range of symptoms from hair loss and brittle nails to more severe neurological and cardiac issues.

Quick Summary

Excessive selenium intake, primarily from supplements or specific foods, leads to selenosis, which manifests with symptoms like garlic breath, fatigue, hair loss, and neurological problems. In severe cases, it can result in organ failure or death. It is important to monitor selenium intake to avoid toxicity.

Key Points

Selenosis Risks: Excessive selenium intake, often from supplements or foods like Brazil nuts, leads to a toxic condition called selenosis.
Key Symptoms: Early signs include garlic-like breath and a metallic taste, followed by hair loss, brittle nails, and gastrointestinal issues.
Serious Complications: Severe cases can result in neurological problems, kidney failure, heart issues, and in rare instances, death.
Supplement Caution: The most common cause is the misuse of selenium supplements; the upper limit for adults is 400 mcg per day.
Treatment Approach: If toxicity is suspected, stop all selenium sources immediately and seek medical advice for supportive treatment, as there is no specific antidote.
Balanced Intake: The best strategy is to obtain selenium from a varied diet rather than relying on high-dose supplements.

What is Selenium and Why is it Essential?

Selenium is a trace mineral that is vital for human health, playing a critical role in metabolism and thyroid function. It is a powerful antioxidant, helping to protect cells from damage caused by free radicals. A healthy intake is important for immune system function, brain health, and reproduction. The amount of selenium found in food depends largely on the soil's selenium content, which varies greatly by region. While many people get sufficient selenium from a balanced diet, some may need supplementation, which is where the risk of overconsumption begins.

Causes of High Selenium Levels (Selenosis)

Selenium toxicity, or selenosis, is primarily caused by excessive intake from dietary supplements or certain foods with very high selenium content. It is not common to develop selenosis from a typical, varied diet. The main culprits are:

Overuse of supplements: The most common cause of selenosis is taking high-dose selenium supplements over a prolonged period. Many people mistakenly believe that if a little is good, more is better, but this is dangerous with minerals like selenium.
Excessive intake of Brazil nuts: Brazil nuts are an exceptionally rich source of selenium, with some nuts containing more than the daily recommended intake. Consuming too many of these regularly can easily lead to toxic levels.
High-selenium soil: In rare cases, individuals living in areas with high-selenium soil can get too much from locally grown foods or contaminated drinking water. This was a known issue in some regions of China and parts of the United States.
Occupational exposure: Workers in certain industries, such as electronics, glass manufacturing, or metal industries, may face higher exposure to selenium dust or volatile compounds.

Symptoms of Selenium Overdose

Symptoms of selenosis can be either acute (from a single high dose) or chronic (from long-term overconsumption) and range from mild to life-threatening. The first signs are often a characteristic garlic-like odor on the breath and a metallic taste in the mouth. Other symptoms include:

Gastrointestinal issues: Nausea, vomiting, and diarrhea.
Hair and nail problems: Hair loss (alopecia), brittle or discolored nails, and nail loss.
Dermatological effects: Skin rashes or lesions.
Neurological issues: Fatigue, irritability, nerve damage (peripheral neuropathy), tremors, and dizziness.
More severe complications: In severe cases, very high doses can lead to heart problems, kidney failure, respiratory distress, and even death.

Comparison of Selenium Deficiency vs. Toxicity


Characteristic	Selenium Deficiency	Selenium Toxicity (Selenosis)
Cause	Insufficient dietary intake, low soil selenium.	Excess intake, primarily from supplements or Brazil nuts.
Common Symptoms	Muscle weakness, altered mental state, suppressed immunity, heart disease.	Garlic breath, metallic taste, hair and nail issues, fatigue.
Associated Conditions	Keshan disease (heart muscle), Kashin-Beck disease (osteoarthritis).	Type 2 diabetes risk, liver and lung damage (severe cases).
Prevalence	Rare in regions with selenium-rich soil like the U.S. and Canada.	Uncommon, but increasing due to supplement misuse.
Resolution	Corrected by increasing dietary intake or supplementation.	Requires discontinuing the selenium source; symptoms resolve over time.

What to Do If You Suspect High Selenium Levels

If you experience symptoms of selenosis, it's critical to take action immediately:

Stop all supplements: Discontinue any selenium-containing supplements immediately.
Evaluate your diet: Review your dietary habits, paying close attention to Brazil nut consumption or other exceptionally high-selenium foods.
Seek medical advice: Consult with a healthcare provider who can order blood or urine tests to measure your selenium levels.
Follow a treatment plan: Treatment typically involves supportive care and managing symptoms while the body naturally eliminates the excess selenium. There is no specific antidote.
Address underlying causes: If the high levels are due to contaminated water or occupational exposure, steps must be taken to address those environmental factors.

Conclusion: Finding the Right Balance is Key

Selenium is a double-edged sword; essential for numerous bodily functions at optimal levels, yet toxic in excess. The key to avoiding selenosis lies in moderation and mindful consumption, particularly when it comes to supplements and very high-selenium foods like Brazil nuts. For most individuals following a balanced diet, supplementation is unnecessary and carries a risk of overdose. By staying informed and consulting with healthcare professionals, you can ensure your selenium intake remains in the safe, beneficial range. For additional information on recommended daily intake and upper limits, the National Institutes of Health provides excellent resources.

Resources

National Institutes of Health (NIH), Office of Dietary Supplements: Provides comprehensive fact sheets on selenium, including recommended intake and upper limits.
MSD Manuals: Offers information on selenium excess and other nutritional disorders.

Frequently Asked Questions

The most common cause is the excessive use of dietary supplements containing selenium, especially when taken in high doses or for extended periods. Overconsumption of foods with exceptionally high selenium content, such as Brazil nuts, can also be a cause.

While it is possible, it is quite rare to get an excess amount of selenium from a typical, balanced diet. The primary food-related risk is from regularly eating large quantities of Brazil nuts, which can contain very high concentrations of the mineral.

Early symptoms of selenium toxicity, or selenosis, often include a distinct garlic-like odor on the breath and a metallic taste in the mouth. These can be followed by gastrointestinal disturbances like nausea and diarrhea.

For adults, the tolerable upper intake level (UL) for selenium is 400 micrograms (mcg) per day from all sources (food, water, supplements). Exceeding this amount significantly increases the risk of toxicity.

Treatment for selenosis primarily involves stopping the source of the excessive selenium intake. For most people, this means discontinuing supplements. Management is supportive and aims to control symptoms while the body naturally clears the excess mineral over time.

Chronic selenosis can lead to severe health issues, including neurological problems such as tremors and numbness, as well as liver and kidney damage. Long-term overexposure has also been associated with an increased risk of developing type 2 diabetes.

Individuals who take high-dose selenium supplements are at the highest risk. Additionally, people living in regions with high soil selenium levels who consume locally grown produce, and those with certain occupational exposures, may also be at higher risk.