What should you not take with selenium?

October 7, 2025 •

4 min read

The recommended dietary intake for selenium is a specific amount per day for adults. Understanding what you should not take with selenium is crucial because this essential trace mineral can interact with various medications and supplements, affecting their efficacy and your health.

Quick Summary

A detailed look at medications and supplements to avoid or use with caution when taking selenium. This covers interactions with blood thinners, statins, chemotherapy drugs, and other vitamins, highlighting potential risks and safety guidelines.

Key Points

Blood Thinners: Selenium can potentially influence blood clotting, which may increase the risk of bleeding when taken with anticoagulants like warfarin or aspirin.
Statins and Niacin: When combined with other antioxidants, selenium may potentially reduce the effectiveness of statins and niacin in improving good cholesterol levels.
Chemotherapy: The interaction is complex; selenium might reduce side effects of some chemo drugs but could also interfere with treatment. Use only under an oncologist's direction.
Potential Toxicity Risk: Consuming amounts above a specific level per day may lead to selenosis, with symptoms like hair loss and garlic breath.
Other Supplements: High intakes of zinc can potentially hinder selenium absorption, while high-intake vitamin C might have a minor effect on the absorption of certain selenium forms.
Immunosuppressants: By potentially influencing the immune system, selenium might counteract the effects of medications designed to suppress it.
Professional Consultation is Crucial: Always consult a healthcare provider before taking selenium supplements due to its potential for interactions.

Selenium is an essential trace mineral vital for many bodily processes, including thyroid hormone metabolism, DNA synthesis, and protection from oxidative damage. While beneficial and necessary in small amounts, its effects can be altered by other substances, and high intakes can be associated with toxicity. Exceeding certain intake levels, especially through supplements, may increase the risk of adverse effects and interactions. Therefore, it's critical to know what substances might negatively interact with selenium.

Key Medication Interactions with Selenium

Always consult a healthcare professional before combining selenium supplements with any prescription medication. Certain drugs can have their effectiveness or side-effect profile altered when taken with selenium.

Medications that Slow Blood Clotting (Anticoagulants/Antiplatelet drugs)

High intakes of selenium might influence blood clotting. Combining it with anticoagulant or antiplatelet drugs could potentially heighten the risk of bruising and bleeding.

Examples: Warfarin (Coumadin), clopidogrel (Plavix), aspirin, heparin, enoxaparin (Lovenox).
Risk: Increased potential for bleeding events. One report noted a critically elevated INR (a measure of blood clotting) in a patient on warfarin after starting a multivitamin containing selenium and vitamin E.

Cholesterol-Lowering Medications (Statins and Niacin)

Selenium, particularly when taken as part of an antioxidant cocktail (with vitamins C, E, and beta-carotene), may interfere with the effectiveness of certain cholesterol medications. This combination might blunt the beneficial effects of statins and niacin on raising high-density lipoprotein (HDL or "good") cholesterol. The effect of selenium alone is not fully clear, but caution is advised.

Examples: Simvastatin (Zocor), atorvastatin (Lipitor), niacin.
Risk: Decreased efficacy of the cholesterol medication.

Sedative Medications (Barbiturates)

Selenium may influence the rate at which the body processes barbiturates. This could potentially affect the effects of these sedative medications.

Risk: Potential for altered sedative effects.

Chemotherapy Drugs

The interaction between selenium and chemotherapy is complex and not fully understood. Some evidence suggests selenium may help reduce the toxicity of certain chemotherapy drugs like cisplatin without compromising efficacy. However, some chemotherapy drugs may also lower selenium levels in the body. Conversely, there is also concern that high-dose antioxidant supplements could interfere with the effectiveness of chemotherapy and radiation. Due to this complexity, cancer patients should never take selenium supplements without explicit guidance from their oncologist.

Immunosuppressants

Selenium may influence the immune system. This action could potentially counteract the intended effect of immunosuppressant drugs, which are prescribed to decrease immune system activity, often after organ transplants.

Examples: Azathioprine (Imuran), cyclosporine (Neoral), tacrolimus (Prograf), and corticosteroids.
Risk: Potential reduction in the effectiveness of the immunosuppressant medication.

Supplement and Mineral Interactions

It's not just prescription drugs that can interact with selenium. Other vitamins and minerals can also affect its absorption and function.

Vitamin C

High intakes of Vitamin C may reduce the body's ability to absorb selenium from certain forms of supplements, although this is not considered a major concern in most cases.

Zinc

High intakes of zinc supplements may interfere with the absorption of selenium from food. The relationship is complex, as studies also show that their functions can be complementary.

Gold Salts

Used in the treatment of rheumatoid arthritis, gold salts can bind to selenium, potentially affecting its levels.

Comparison Table: Selenium Interactions


Interacting Substance	Type	Potential Risk	Recommendation
Warfarin, Plavix, Aspirin	Anticoagulant/Antiplatelet	Increased risk of bleeding.	Consult a doctor; monitor for bruising or bleeding.
Statins (e.g., Simvastatin) & Niacin	Cholesterol Medication	May reduce the drug's effectiveness in raising 'good' cholesterol.	Discuss with your healthcare provider.
Cisplatin	Chemotherapy Drug	Complex interaction; may reduce drug toxicity but also potentially interfere.	Strictly under oncologist supervision only.
Immunosuppressants	Immune-suppressing Drug	May decrease the medication's effectiveness.	Consult a doctor before use.
High-Intake Vitamin C	Vitamin Supplement	Can potentially reduce selenium absorption from some forms.	Generally not a major concern, but be mindful of high intakes.
High-Intake Zinc	Mineral Supplement	May interfere with selenium absorption from food.	Avoid taking very high intakes of zinc simultaneously.

Signs of Potential Selenium Toxicity (Selenosis)

Consuming amounts of selenium exceeding certain levels, typically from supplements rather than food, has been associated with a condition called selenosis. Chronic potential toxicity may occur with intakes above a specific amount per day.

Common symptoms include:

Garlic-like odor on the breath and a metallic taste in the mouth
Hair loss
Nail brittleness, discoloration, or loss
Nausea and diarrhea
Fatigue and irritability
Skin rashes
Nerve damage (peripheral neuropathy)

In a 2008 outbreak caused by a misformulated supplement, the most frequently reported symptoms were diarrhea (78%), fatigue (75%), and hair loss (72%).

Conclusion

Selenium is a crucial nutrient, but maintaining the right balance is key. It has a narrow window between beneficial and potentially excessive intake. Because selenium can interact with common medications like blood thinners and statins, as well as other supplements, it is imperative to speak with a healthcare provider or pharmacist before starting selenium supplementation. They can assess your individual health status, current medications, and diet to determine if supplementation is safe and necessary for you. Never self-prescribe high intakes of selenium, especially if you have underlying health conditions or are taking any prescription drugs.

For more information from an authoritative source, you can visit the National Institutes of Health (NIH) Office of Dietary Supplements Fact Sheet on Selenium: https://ods.od.nih.gov/factsheets/Selenium-HealthProfessional/

Frequently Asked Questions

It is not recommended without medical supervision. Selenium might influence blood clotting, and taking it with blood thinners like warfarin can potentially increase the risk of bruising and bleeding.

You should be cautious. Selenium, especially in combination with other antioxidants, might decrease the effectiveness of statins and niacin at raising your 'good' cholesterol levels. Consult your doctor.

High intakes of vitamin C might slightly reduce the absorption of some forms of selenium, but this is generally not considered a significant issue for most people.

Signs associated with excessive selenium intake (selenosis) often include a garlic-like odor in the breath, a metallic taste in the mouth, hair loss, and nail brittleness or discoloration.

The tolerable upper intake level (UL) for adults is a specific amount per day from all sources, including food and supplements. Consuming more than this on a regular basis may be associated with toxicity.

Yes, it's possible. Check the levels of selenium, zinc, and vitamin C in your multivitamin. Very high intakes of zinc can potentially interfere with selenium absorption. Consider all selenium sources to help stay within recommended limits.

Given that selenium can potentially influence blood clotting, it is wise to discuss your supplement use with your surgeon. They may advise you on appropriate timing for taking it, along with other supplements like vitamin E and fish oil, before your procedure to help manage bleeding risk.