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Overview: Selenium is a mineral that is commonly used to prevent or treat low levels of selenium in the body. It is available over the counter as a supplement and is usually well tolerated. But taking too much selenium can be harmful. Before taking selenium, tell your health care provider about all of your health conditions and any medicines or supplements you may be using.

Uses

What is selenium used for?

Selenium is commonly used to prevent or treat low levels of selenium from various causes.

Selenium may also be used for other conditions as determined by your health care provider.

Selenium is available as a dietary supplement in various strengths and dosage forms. It is also found as an ingredient in some multivitamins or in vitamin E supplements.

Note: The FDA has not reviewed selenium for safety and effectiveness. Learn more about dietary supplements here.

How does selenium work (mechanism of action)?

Selenium is an essential trace mineral. This means that your body needs it to function, but only in very small amounts. Your body uses selenium to make selenoproteins, which are substances that play an important role in making DNA and certain hormones. Selenoproteins are also antioxidants that help protect your cells from damage.

In the U.S., most people get enough selenium from their diet. It is found in many foods, especially those that are high in protein, such as meat, seafood, nuts, and dairy products, and whole grains. For most adults, the recommended daily intake of selenium is 55 micrograms (mcg). However, some people either do not get enough from their diet or have trouble absorbing it. When this happens, you can take selenium to replace what you are not getting from your diet.

How should I store selenium?

You should store selenium according to the product label. Most dietary supplements should be kept in a cool, dry location that is out of the reach of children and pets and not in direct sunlight.

Side Effects

What are the most common side effects of selenium?

Selenium seems to be well tolerated. Tell your health care provider if you have any side effects that bother you.

There may be side effects of selenium that are not listed here. Contact your health care provider if you think you are having a side effect of a supplement. In the U.S., you can report side effects to the FDA at www.safetyreporting.hhs.gov or by calling 888-SAFEFOOD (888-723-3366). In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

What are the serious side effects of selenium?

While less common, the most serious side effects of selenium are described below, along with what to do if they happen.

Severe Allergic Reactions. Selenium may cause allergic reactions, which can be serious. Stop taking selenium and get help right away if you have any of the following symptoms of a serious allergic reaction.

  • Breathing problems or wheezing
  • Racing heart
  • Fever or general ill feeling
  • Swollen lymph nodes
  • Swelling of the face, lips, mouth, tongue, or throat
  • Trouble swallowing or throat tightness
  • Itching or skin rash
  • Bumps on the skin called hives that can be red, pink, white, or brown depending on your skin tone
  • Nausea or vomiting
  • Dizziness, feeling lightheaded, or fainting
  • Stomach cramps
  • Joint pain

Warnings & Precautions

Who should not use selenium?

Allergies to Ingredients. People who are allergic to any of the following should not take selenium.

  • Selenium (Se)
  • Selenomethionine
  • Sodium selenate
  • Sodium selenite
  • Any of the ingredients in the specific product

Your pharmacist can tell you all of the ingredients in the specific selenium products they stock.

What should I know about selenium before using it?

Selenium is a dietary supplement. It cannot be marketed to treat or cure a disease.

Read and follow the directions on the specific product you are taking, or take it as recommended by your health care provider.

Keep selenium out of the reach of children.

Dietary supplements may contain many forms of selenium, such as selenomethionine, sodium selenate, and sodium selenite. Some dietary supplements contain selenium-enriched yeast, which is sometimes listed on the label as selenium yeast. This means that the yeast (a type of fungus) was grown in a broth containing high amounts of selenium. All of these different forms of selenium are absorbed by your body the same way.

You can get selenium from several places, including foods and other vitamins or supplements. Many multivitamin and combination supplement products have selenium in them. Certain foods, such as Brazil nuts, contain especially high amounts of selenium. It is important not to take too much selenium. Too much selenium can be harmful. If you are not sure how much selenium you need or if you need a selenium supplement, talk to your health care provider.

The FDA has not tested selenium products to confirm that they contain the ingredients stated on their labels. Some dietary supplements have been tested by third-party organizations to confirm that they contain the ingredients listed on their labels and do not contain any harmful chemicals. Learn more about how to choose a safe dietary supplement product here.

What should I tell my health care provider before using selenium?

Tell your health care provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. This will help them know if selenium is right for you.

In particular, make sure that you discuss any of the following.

Yeast Allergy. Some selenium supplements contain selenium-enriched yeast. If you have a yeast allergy, only choose selenium supplements that are labeled as yeast-free. Speak with your health care provider if you have any questions or concerns.

Other Current and Past Health Conditions. Tell your health care provider if you have any of the following.

  • Thyroid problems
  • Low iodine levels
  • Kidney problems, including if you are receiving dialysis
  • HIV or AIDS

Other Medicines and Supplements. Selenium may interact with other medicines and supplements. Before taking selenium, tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. See the Interactions section for more details.

Pregnancy. It is not known if or how selenium could affect pregnancy or harm a fetus. Tell your health care provider if you are pregnant or plan to become pregnant.

Breastfeeding. Selenium passes into breast milk. Tell your health care provider if you are breastfeeding or plan to breastfeed.

Interactions

Does selenium interact with foods or drinks?

There are no known interactions between selenium and foods or drinks.

It is unknown if drinking alcohol will affect selenium.

Does selenium interact with medicines (drug interactions)?

Always tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using.

In particular, make sure that you discuss if you are using cisplatin, which is a type of medicine to treat cancer.

The interactions between selenium and medicines are not fully understood. As with most dietary supplements, the research on drug interactions with selenium is incomplete. Always check with your health care provider before taking selenium with any medicines.

Overdose/Missed Dose

What should I do if I accidentally use too much selenium?

If you or someone else has used too much selenium, get medical help right away, call 911, or contact a Poison Control center at 800-222-1222.

Selenium is found in many foods, sometimes in high amounts. It may be found in dietary supplements as a single ingredient and in some multivitamin products. Read the product label closely, and speak with a health care provider about how to take selenium safely. Do not take double or extra doses, even if you miss a dose.