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Make sure to tell your healthcare provider about all existing medical conditions you have and other medications you are taking before starting selenium. Safety precautions also include watching out for possible drug interactions and using selenium with caution if you are pregnant or breastfeeding. Selenium supplements may not be safe for people who have an underactive thyroid, certain allergies, or skin cancer.
Is Selenium Safe? -- An OverviewSelenium may provide numerous health benefits, but it can also cause dangerous side effects, especially if taken at high doses. Some people are more likely than others to experience problems due to selenium. You should talk with your healthcare provider prior to taking it if you have:
- An underactive thyroid (hypothyroidism)
- Male infertility
- Skin cancer (or a history of skin cancer)
- Any allergies, including allergies to foods, dyes, or preservatives.
- Pregnant or thinking of becoming pregnant
Specific Selenium Safety Precautions and WarningsSome of the warnings and precautions to be aware of concerning the safety of selenium include the following:
- Most people in the United States get plenty of selenium through dietary means. A high selenium intake can cause serious toxicity -- and even death.
- Selenium supplementation in people who have an underactive thyroid due to iodine deficiency can actually make their thyroid problems worse. If you have iodine deficiency, do not take selenium supplements without your healthcare provider's approval.
- Some (but not all) research suggests that a long-term intake of high doses of selenium may increase the risk of skin cancer. If you have skin cancer or a history of skin cancer, it is a good idea to avoid selenium supplements until more information is known.
- Some research suggests that a high selenium intake can decrease sperm motility. If you are a male with infertility problems, it is probably a good idea to avoid selenium supplements.
- Selenium supplements are not as closely regulated as prescription and non-prescription drugs. Therefore, they can be marketed without any proof that they are either safe or effective. Do not assume that just because a product is sold in the United States that it is safe or effective. Be sure to look for selenium supplements that are made by a reputable manufacturer. Your pharmacist is a good resource for information about which manufacturers are the most reputable.
- Selenium may potentially interact with some medications (see Selenium Drug Interactions).
- Normal dietary intakes of selenium are safe and beneficial for pregnant and breastfeeding women. However, it is not known if higher doses are safe (see Selenium and Pregnancy and Selenium and Breastfeeding).