Along with its needing effects, a dietary supplement may cause some unwanted effects. Although selenium supplements have not been reported to cause any side effects, check with your health care professional immediately if any of the following side effects occur as a result of an overdose:
Symptoms of overdose
Diarrhea; fingernail weakening; garlic odor of breath and sweat; hair loss; irritability; itching of skin; metallic taste; nausea and vomiting; unusual tiredness and weakness
More common side effects not listed above may also occur in some individuals. If you notice any other problems, check with your health care professional.