ingestible · for thyroid support
Selenium
Reviewed by the Nimbera editorial team · Last updated May 2026
How to use
Take 200 mcg of selenomethionine daily with food. This is the form and dose used in most clinical trials. Brazil nuts naturally contain selenium (1-2 nuts per day provide approximately 100-200 mcg) but content varies widely by soil. Confirm selenium status with serum selenium or selenoprotein P testing before long-term supplementation.
How it works
Selenium is a cofactor for selenoprotein enzymes including glutathione peroxidase and deiodinases - enzymes that convert T4 to the active T3 hormone and protect the thyroid gland from oxidative damage during hormone synthesis. Hashimoto's thyroiditis involves autoimmune attack on the thyroid; selenium may reduce this through anti-inflammatory mechanisms.
Where to buy
Pharmacies and health food stores. Look for selenomethionine (organic form, best absorbed). Yeast-bound selenium is also acceptable. Avoid sodium selenite at high doses.
Typical cost: $10-$20 per month.
Safety notes
CAUTION: Selenium is toxic in excess. The upper tolerable limit is 400 mcg/day for adults - do not exceed this. Chronic excess causes selenosis: hair loss, nail brittleness, garlic breath, neurological effects, and in severe cases liver failure. Do not combine selenium supplements with Brazil nut consumption without calculating total daily intake. Selenium supplementation evidence is specifically for people with autoimmune thyroiditis (Hashimoto's) - not general hypothyroidism. Requires medical supervision.
Drug & supplement interactions
- Always tell your doctor or pharmacist about any supplements you take.
- Interactions can occur with prescription medications, blood thinners, and immunosuppressants.
- Herbal remedies can affect how the body absorbs or metabolises drugs.
- Check drugs.com interactions checker before starting.
Clinical source
Sut & Simsek-Yavuz. Thyroid 2024 - PMID 38243784This information is compiled from primary clinical literature and is for informational purposes only. It is not a substitute for professional medical advice. Read our full disclaimer.