Selenium Supplements: Benefits, Dosage and Safety
Selenium supplements are rarely needed because most diets provide enough. In Hashimoto's thyroiditis, selenium lowered thyroid antibodies in some meta-analyses, without clear benefits for symptoms. Too much selenium causes hair and nail loss and other toxicity.
Evidence at a glance
| Use | Grade | What the research shows |
|---|---|---|
| Lowering thyroid antibodies in Hashimoto's | C | Some meta-analyses show lower antibodies; symptoms unclear. |
| Preventing prostate cancer | D | The SELECT trial found no benefit. |
A: strong, consistent human evidence · B: moderate · C: limited or mixed · D: good evidence of no benefit.
Selenium is part of enzymes that protect cells and help activate thyroid hormone.
How to take it
Studies in Hashimoto's used 100–200 mcg a day. Discuss with your doctor first. See thyroid supplements.
Safety and interactions
Stay under 400 mcg a day from all sources. Signs of excess include garlic breath, brittle nails and hair loss.
Always tell your doctor and pharmacist about the supplements you take. Check combinations with our interaction checker.
Sources
This page is for education and is not a substitute for advice from your doctor. Read our medical disclaimer.