Reviewed on 9/17/2021

What Is Selenium and How Does It Work?

Selenium is a trace element that is naturally present in many foods, added to others, and available as a dietary supplement. Selenium is nutritionally essential for humans plays a critical role in reproduction, thyroid hormone, metabolism, DNA synthesis, and protection from oxidative damage and infection.

Selenium is available under the following different brand names: Selepen.

What Are the Dosages of Selenium?

Dosages of Selenium Should Be Given As Follows:


  • 50 mcg
  • 100 mcg
  • 125 mcg
  • 200 mcg

Tablets, Extended Release

  • 200 mcg


  • 200 mcg

Injectable Solution

  • 40 mcg/mL

Dosage Considerations

Recommended Daily Allowance - Adults

  • Male or female: 55 mcg/day
  • Pregnancy: 60 mcg/day
  • Lactating: 70 mcg/day

Recommended Daily Allowance - Adults

  • 100-200 mcg/day orally preferably with meals; may take 50 mcg orally once a day or every 6 hours.

Recommended Daily Allowance - Pediatric

  • Under 6 months: 15 mcg/day
  • 6-12 months: 20 mcg/day
  • 1-3 years: 20 mcg/day
  • 4-8 years: 30 mcg/day
  • 8-13 years: 40 mcg/day
  • 13-18 years: 55 mcg/day


About how much does an adult human brain weigh? See Answer

What Are Side Effects Associated with Using Selenium?

Side effects associated with the use of selenium includes the following:
  • irritability

This document does not contain all possible side effects and others may occur. Check with your physician for additional information about side effects.

What Other Drugs Interact with Selenium?

If your doctor has directed you to use this medication, your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with your doctor, health care provider, or pharmacist first.

  • Selenium has serious interactions with the drug eltrombopag.

This document does not contain all possible interactions. Therefore, before using this product, tell your doctor or pharmacist of all the products you use. Keep a list of all your medications with you, and share the list with your doctor and pharmacist. Check with your physician if you have health questions or concerns.

What Are Warnings and Precautions for Selenium?


  • This medication contains selenium. Do not take Selepen if you are allergic to selenium or any ingredients contained in this drug.
  • Keep out of reach of children. In case of overdose, get medical help or contact a Poison Control Center immediately.


  • Do not inject undiluted selenium into a peripheral vein.

Effects of Drug Abuse

  • There are no effects of drug abuse with the use of selenium.

Short-term Effects

  • There are no short-term effects from the use of selenium.

Long-term Effects

  • There are no long-term effects from the use of selenium.


  • There are no cautions associated with the use of selenium.

Pregnancy and Lactation

  • Do not take selenium when pregnant or if lactating.
Medscape. Selenium.
National Institutes of Health Office of Dietary Supplememts.

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