Key takeaways
The 30-second version
- Selenium has its strongest Graves' evidence in mild thyroid eye disease: a 6-month course helped in the major European trial (Grade B).
- For the overactive thyroid itself, selenium may help hormone levels short term alongside methimazole, but there is no proof it improves long-term remission (Grade C).
- The trial dose was 100 mcg twice a day for 6 months. Do not go above 400 mcg a day in total.
- Selenium is an add-on. It never replaces antithyroid medication, and quitting smoking matters more for the eyes.
- Tell your endocrinologist before starting. Eye pain, double vision or sight changes need urgent medical care.
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Take the 3-min quiz →Selenium has moderate-quality evidence in Graves' disease, mainly for mild thyroid eye disease (Graves' orbitopathy), and weaker, short-term evidence as an add-on to antithyroid drugs. The best trial is the European EUGOGO study (Marcocci et al., NEJM 2011), in which 6 months of selenium improved quality of life and eye outcomes in mild orbitopathy. It is not a treatment for hyperthyroidism on its own. This guide compares selenium in Graves' with selenium in Hashimoto's, covers dose and safety, and flags when to see a specialist. For the broader picture see Graves' disease natural treatment, and for the Hashimoto's evidence see selenium for Hashimoto's.
Why Graves' and Hashimoto's Differ
In Hashimoto's, the immune system destroys thyroid tissue, and selenium's job is largely reducing thyroid antibodies and oxidative stress. In Graves', antibodies stimulate the thyroid receptor (TRAb), causing hyperthyroidism, and can also inflame tissue around the eyes. Selenium is part of the antioxidant enzymes (glutathione peroxidases) that handle oxidative stress in both thyroid and orbital tissue. That is the rationale. The clinical questions differ, so the evidence has to be read separately. Selenium is not an immune stimulant, which is one reason it is the supplement endocrinologists most often discuss for Graves'. Other thyroid "supports" are riskier here. See Graves' disease natural treatment.
The Evidence
Mild Thyroid Eye Disease (Graves' Orbitopathy)
In the EUGOGO randomised trial (Marcocci et al., NEJM 2011), 159 patients with mild orbitopathy received selenium 100 mcg twice daily, pentoxifylline 600 mg twice daily or placebo for 6 months, then were followed for 6 months off treatment. At 6 months, selenium (but not pentoxifylline) was associated with better quality of life (P below 0.001), less eye involvement (P=0.01) and slower progression (P=0.01). A 12-month evaluation supported these findings. No adverse events were evident with selenium.
The 2016 ETA/EUGOGO guideline included a 6-month selenium course for mild orbitopathy. The American Thyroid Association has not endorsed the recommendation. The trial was run in a region with relatively low dietary selenium, so benefits may be smaller if your intake is already adequate.
Grade: B (one well-run RCT, supported by guideline use, with a region-specific caveat).
Selenium With Antithyroid Drugs
Randomised trials of selenium added to methimazole include small placebo-controlled studies in Sweden (a selenium-deficient region) and Germany (selenium-sufficient). A 2018 meta-analysis (Zheng et al.) found lower free T4 and free T3 at 3 months with selenium than placebo, and patients given selenium were more likely to have improved thyroid function at 6 months, but that benefit had disappeared by 9 months. Reviews (Bednarczuk and Schomburg, 2019) conclude that the evidence is ambiguous and that long-term outcomes such as remission are largely missing. Benefit may depend on baseline selenium status.
Grade: C for hyperthyroidism control and remission.
| Use | Best evidence | Grade |
|---|---|---|
| Mild Graves' orbitopathy | Marcocci 2011 NEJM, EUGOGO, 159 patients | B |
| Faster normalisation of thyroid hormones with methimazole | 2018 meta-analysis of small RCTs; benefit gone by 9 months | C |
| Higher remission rates after stopping drugs | Not established | C |
For another Graves' option under study, see low-dose naltrexone for Graves' disease.
Dose, Form and Safety
- Trial dose: 100 mcg twice daily for 6 months (EUGOGO). Discuss any dose with your endocrinologist.
- Upper limit: the US adult tolerable upper intake level is 400 mcg per day from all sources. Selenosis (hair and nail changes, garlic breath, GI upset) is a risk above this.
- Count your sources: multivitamins, thyroid formulas and Brazil nuts all contribute. One Brazil nut can contain very different amounts.
- Form: supplement forms vary (selenomethionine, sodium selenite, selenium-enriched yeast). The best-evidenced orbitopathy dose is from the trial protocol, so ask your doctor which product to use.
- Interaction with methimazole: no interaction has been reported in trials, but your prescriber should know, because they monitor your thyroid labs and dose.
- Stop and ask if you develop nausea, brittle nails or hair loss.
For zinc and vitamin D roles in thyroid disease see zinc and the thyroid and vitamin D and the thyroid.
Who Should Not Self-Start
- Anyone with untreated or uncontrolled hyperthyroidism. This needs medical treatment first.
- People with moderate to severe or sight-threatening eye disease. Selenium is not enough.
- Smokers. Smoking is the best-established modifiable risk factor for orbitopathy. Quitting matters more than any supplement.
- People taking other selenium-containing products or with known high selenium intake.
- Pregnant people, who should follow obstetric and endocrine advice.
Red Flags for Thyroid Eye Disease
Seek urgent medical care for double vision, pain with eye movement, a change in colour vision, blurred vision, or a bulging eye that cannot close. These can threaten sight.
Next Steps
- Book or keep your endocrinology appointment, and ask about eye assessment.
- If you have mild orbitopathy, ask whether a 6-month selenium course fits your case.
- Keep taking prescribed antithyroid drugs.
- Recheck thyroid labs on your clinician's schedule.
Take the free 3-minute AutoimmuneFinder quiz for a personalized, evidence-graded protocol.
Frequently Asked Questions
Does selenium help Graves' disease?
Best for mild thyroid eye disease (Grade B). For hyperthyroidism, benefit is short term and remission effects are unproven (Grade C).
How much selenium for Graves' orbitopathy?
The trial used 100 mcg twice daily for 6 months. Discuss with your endocrinologist, and keep total intake under 400 mcg a day.
Can I take selenium with methimazole?
No interaction was reported in trials, but tell your endocrinologist. Selenium never replaces methimazole.
Is selenium safe in thyroid eye disease?
No adverse events were evident in the main trial at the studied dose. Eye pain or sight changes need urgent medical review.
This site provides educational information only. Not medical advice. Always consult your healthcare provider before changing your treatment plan.