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Higher doses can cause significant side effects including nausea, vomiting, nail changes, loss of energy, and irritability. Poisoning from long-term use is similar to arsenic poisoning, with symptoms including hair loss, white horizontal streaking on fingernails, nail inflammation, fatigue, irritability, nausea, vomiting, garlic breath odor, and a metallic taste.
Selenium can also cause muscle tenderness, tremor, lightheadedness, facial flushing, blood clotting problems, liver and kidney problems, and other side effects.
There is also concern that taking selenium for a long time might not be safe.
Some research shows that long-term use of selenium supplements might increase the risk for skin cancer recurrence. Until more is known, people who have had skin cancer should avoid selenium supplements.
There is also concern that taking large amounts of a multivitamin plus a separate selenium supplement might increase the chance of developing prostate cancer and dying from prostate cancer.
Long-term consumption of selenium supplements also appears to increase the chance of getting type 2 diabetes.
Do not take selenium if:
Report Problems to the Food and Drug Administration
You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.