Is it Bad to Take Selenium Every Day? Understanding the Risks and Optimal Intake

November 4, 2025 •

4 min read

The average daily selenium intake for adults aged 19 and older is 55 micrograms (mcg), but the amount can vary greatly depending on diet and geographic location. Knowing your personal selenium status is crucial, as the answer to 'is it bad to take selenium every day?' depends entirely on your needs and dosage.

Quick Summary

Taking selenium every day is not inherently bad, but the risk of toxicity increases with high doses and long-term use. Effects range from mild side effects to severe health issues. Dosage must be balanced, as the line between beneficial and harmful can be narrow.

Key Points

Narrow Therapeutic Window: The difference between a beneficial and a toxic dose of selenium is small, making consistent, high-dose daily supplementation risky.
Toxicity Risks: Symptoms of excessive intake (selenosis) include garlic breath, hair loss, nail changes, fatigue, and potential organ damage at very high doses.
Chronic Disease Concerns: Long-term, high-dose selenium has been linked to an increased risk of type 2 diabetes and certain skin cancers in non-deficient individuals.
Evaluate Your Needs: Most people can get enough selenium from food sources. Supplementation is typically only necessary for those with documented deficiencies or specific medical conditions.
Medical Guidance is Key: Always consult a healthcare professional before starting daily selenium supplements to determine if they are safe and necessary for you.
Watch for Interactions: Selenium can interact with certain medications, including anticoagulants and statin drugs.
Food Sources: Excellent sources include Brazil nuts, fish, seafood, and lean meats, but the selenium content varies by soil region.

The Double-Edged Sword of Daily Selenium Intake

Selenium is an essential trace mineral vital for numerous bodily functions, including antioxidant defense, thyroid hormone metabolism, and immune system function. It is incorporated into selenoproteins, which have diverse roles in protecting cells from damage and supporting overall health. For most people, adequate selenium is obtained through a balanced diet, but supplementation has become popular. The critical question, therefore, is whether consistent daily supplementation poses risks.

The key to understanding if taking selenium every day is bad lies in a principle of nutrition: the dose makes the poison. There is a narrow window between beneficial levels of selenium and levels that can lead to toxicity, a condition known as selenosis. While deficiency can lead to severe health issues like Keshan disease or Kashin-Beck disease, excessive intake can be equally, if not more, dangerous.

Risks of Long-Term Excessive Selenium Intake

Taking high doses of selenium every day, particularly via supplements, can lead to a build-up in the body and cause adverse health effects. The European Food Safety Authority (EFSA) sets a Tolerable Upper Intake Level (UL) of 255 mcg/day for adults, with the US National Institutes of Health (NIH) setting its UL at 400 mcg/day. Consistently exceeding these limits can lead to chronic toxicity.

Early Signs and Symptoms of Selenosis

Garlic-like breath odor
Hair loss (alopecia)
Brittle or discolored nails
Gastrointestinal upset, including nausea and diarrhea
Skin rashes or lesions
Chronic fatigue and irritability

Severe Complications from High Doses

In extreme cases, high selenium intake can lead to serious health problems, including respiratory distress, heart failure, kidney failure, and neurological damage. It is also associated with an increased risk of certain conditions, especially with long-term use.

Type 2 Diabetes: Studies have shown a correlation between high selenium intake over many years and an increased risk of developing type 2 diabetes, particularly in individuals with already sufficient selenium levels.
Skin Cancer: Some research suggests a potential link between long-term selenium supplementation and an increased risk of nonmelanoma skin cancer (specifically squamous cell carcinoma) in individuals who are not deficient.
Prostate Cancer: The Selenium and Vitamin E Cancer Prevention Trial (SELECT) found that selenium supplementation did not prevent prostate cancer and, in some cases, slightly increased the risk in men with high baseline selenium.

Who Should Be Cautious About Daily Selenium?

While some people might benefit from targeted, temporary selenium supplementation, others should approach daily intake with caution or avoid it entirely unless advised by a doctor. This includes individuals with certain pre-existing conditions or those on specific medications.

Autoimmune Diseases: Selenium can stimulate the immune system, which could worsen symptoms in individuals with autoimmune conditions such as lupus or rheumatoid arthritis.
Hypothyroidism with Iodine Deficiency: High selenium can exacerbate hypothyroidism in individuals with an underlying iodine deficiency. It's crucial to address iodine levels alongside selenium.
Skin Cancer History: As mentioned, long-term use is not advised for those with a history of nonmelanoma skin cancer.
Before Surgery: Selenium can slow blood clotting. It's recommended to stop supplementation at least two weeks before scheduled surgery.
Medication Interactions: Selenium can interact with certain medications, including anticoagulants, some chemotherapy drugs, statins, and oral contraceptives.

Supplement Forms: A Comparison

Selenium supplements come in various forms, and their absorption and potential effects can differ. The form, dosage, and a person’s baseline selenium status are all important factors to consider before starting daily intake.


Feature	Selenomethionine	Selenium-Enriched Yeast	Sodium Selenite	Sodium Selenate
Absorption Rate	Very high (approx. 90%)	High (rich in selenomethionine)	High	High
Organic/Inorganic	Organic	Organic	Inorganic	Inorganic
Incorporation into Proteins	Can be non-specifically incorporated into proteins, acting as a storage form.	Primary form is selenomethionine, similar benefits to pure selenomethionine.	Does not get non-specifically incorporated; converts to selenocysteine.	Does not get non-specifically incorporated; converts to selenocysteine.
Safety Profile	Generally considered safe at appropriate doses.	Safe at appropriate doses, but high amounts of organic selenium from food can be a concern.	Effective, but can be slightly more toxic than organic forms at high doses.	Effective, potentially less toxic than selenite.

Determining Your Need: Diet vs. Supplements

For most healthy adults, daily selenium needs (RDA of 55 mcg) can be easily met through diet. The selenium content in foods varies greatly depending on the soil content where they were grown. Excellent food sources include Brazil nuts (extremely high), fish, seafood, lean meats, poultry, eggs, cottage cheese, and certain grains.

Key considerations for daily selenium supplementation:

Geographic location: Individuals in regions with selenium-deficient soil may need supplementation.
Underlying health issues: A doctor might recommend supplementation for specific conditions like documented deficiencies, certain thyroid issues, or male fertility problems.
Blood testing: The most reliable way to know if you are deficient is to have a blood test. Unnecessary supplementation in individuals with sufficient levels may be harmful.

Conclusion

While taking selenium every day is not automatically bad, it is only recommended for those with a confirmed deficiency or a specific medical reason, and under a doctor's supervision. The mineral's narrow therapeutic window means that excessive, long-term daily intake from supplements can lead to toxicity, with symptoms ranging from hair loss to more serious health complications. Before starting any daily regimen, assess your dietary intake and, if necessary, consult a healthcare professional. Ensuring you stay within safe limits and don't take more than you need is the most responsible approach to maintaining a healthy selenium status. For more information, the National Institutes of Health (NIH) Office of Dietary Supplements provides a comprehensive consumer fact sheet.

Frequently Asked Questions

The recommended dietary allowance (RDA) for most adults aged 19 and older is 55 micrograms (mcg) per day. For pregnant women, it's 60 mcg, and for breastfeeding women, it's 70 mcg.

Early symptoms of selenium toxicity often include a garlic-like odor on the breath, a metallic taste in the mouth, brittle hair and nails, skin rashes, and fatigue.

Yes, it is possible, though rare. Brazil nuts, for example, are extremely high in selenium, and eating just a few per day can push you over the safe upper limit. However, most people primarily get selenium from a variety of other, less concentrated food sources.

Yes, excessive intake of selenium, often from daily supplements, is a known cause of hair loss. This is a common symptom of selenosis, or selenium toxicity.

People with autoimmune diseases, a history of nonmelanoma skin cancer, or those with underlying thyroid issues should be cautious. Additionally, people taking certain medications, such as blood thinners, should consult a doctor before supplementing.

Your selenium levels can be checked with a blood test. Plasma and serum concentrations reflect recent intake, while whole blood and nail samples indicate long-term status.

If you stop taking selenium supplements, your levels will gradually decrease. For those with toxicity, this will allow your body to excrete the excess selenium and alleviate symptoms. If you have a deficiency, your levels will eventually drop back down without continued supplementation.

The body absorbs both organic (e.g., selenomethionine from yeast) and inorganic (e.g., sodium selenite) selenium efficiently. Organic forms can be stored more easily, while inorganic forms are more readily available for immediate use by selenoproteins. The best form depends on individual needs and a doctor's guidance.