No human trial has tested reishi, lion's mane, cordyceps, chaga or any other medicinal mushroom for thyroid function. Not one. Yet mushrooms and the thyroid do meet in real, practical ways: at breakfast, when a capsule or a mushroom coffee lands next to a levothyroxine tablet; in the lab, when a "hair, skin and nails" blend skews a blood test; and on the label, when a product sold for one thing quietly contains iodine or biotin. Those intersections matter far more than any claim about "thyroid support".
There's no clinical evidence that any medicinal mushroom improves or harms thyroid function. The real issues are practical. Most edible mushrooms are selenium-poor, under 1 µg per gram of dry weight according to Falandysz's review of 190 species. Levothyroxine is absorbed in microgram amounts, so the NHS advises taking it on an empty stomach 30 to 60 minutes before food, caffeine or other medicines; that includes mushroom coffee and capsules. High-dose biotin, common in beauty blends, interfered with 9 of 23 biotin-based lab assays in a 2017 JAMA study. And mushrooms aren't an iodine source, unlike sea moss.
This is a safety guide, not a sales page. It covers what's known, what isn't, and what to tell your prescriber if you take both thyroid medication and mushroom supplements.
Is There Any Evidence That Mushrooms Affect the Thyroid?
Not directly. There's no randomised trial, cohort study or registry of any common medicinal mushroom in people with an underactive or overactive thyroid, and none measuring TSH or thyroid hormones as an outcome. Our review of mushrooms and autoimmune conditions reached the same conclusion for Hashimoto's thyroiditis specifically.
That absence cuts both ways. It means any product promising "thyroid support" from reishi or lion's mane is making a claim nobody has tested. It also means there's no evidence that these mushrooms damage the thyroid. What we can discuss with evidence is the chemistry around them: minerals, absorption, lab interference and the other ingredients that share the capsule.
Are Mushrooms a Good Source of Selenium?
Mostly not. Falandysz's 2008 review compiled selenium data for 190 mushroom species and found that most edible species examined were selenium-poor, below 1 µg per gram of dry weight. A few wild species are exceptions. The goat's foot mushroom (Albatrellus pes-caprae) averaged around 200 µg/g, with a maximum of 370, and the king bolete (Boletus edulis) averaged about 20 µg/g.
None of the usual supplement species appears in that short list of naturally rich mushrooms. The review's one reishi figure comes from selenium-enriched cultivation: Ganoderma lucidum grown on a substrate fortified with selenium could reach 72 µg/g. So a "selenium reishi" is a deliberately different product from ordinary reishi, and it should say so on the label. At under 1 µg/g, a gram or two of standard mushroom powder contributes very little selenium to your day.
Why does selenium come up at all?
Because it's the thyroid nutrient with the most trial data. Wichman and colleagues' 2016 meta-analysis of 16 controlled trials in chronic autoimmune thyroiditis found that selenium supplementation lowered thyroid peroxidase antibody (TPOAb) levels at 3, 6 and 12 months in people already taking levothyroxine. Two caveats sit in the same abstract. The quality of evidence was generally low, and people taking selenium reported adverse effects significantly more often than controls. Most importantly, the authors wrote that whether lower antibody levels translate into clinically relevant benefits remains to be demonstrated.
So even the thyroid nutrient with real trials hasn't shown it makes patients better, and mushrooms don't supply much of it anyway. If you're considering selenium for a thyroid condition, that's a decision for your endocrinologist, not a reason to buy mushrooms.
How Should You Time Mushroom Supplements Around Levothyroxine?
Keep them apart. Levothyroxine is dosed in micrograms and has a narrow therapeutic index, which is why Skelin and colleagues' 2017 review describes absorption interactions as clinically significant. The review found that coffee and soybeans had the greatest impact on reducing absorption, and that calcium carbonate, calcium citrate, iron sulfate, proton pump inhibitors and several other drugs cause an established, clinically significant decrease when taken at the same time.
The mechanism is mostly physical: levothyroxine binds to the interfering substance in the gut, leaving less available to absorb. The review's remedy is equally simple. Separate the two. The NHS gives the practical version: take levothyroxine on an empty stomach, 30 to 60 minutes before your first meal, any caffeinated drink such as tea or coffee, or any other medicine, at the same time each day.
Nobody has studied mushroom powders and levothyroxine together. Mushrooms are fibre-rich, and Skelin's review says the effect of dietary fibre on absorption isn't fully understood yet. That's not proof of a problem. It's a reason not to take the two together when separating them costs nothing.
What about mushroom coffee?
This is the realistic breakfast collision. A mug of "mushroom coffee" first thing in the morning combines coffee, which the review ranks among the biggest absorption reducers, with an untested fibre-rich powder. If you drink it, have it at least as long after your tablet as your prescriber advises for ordinary coffee. The mushroom isn't the known problem there; the coffee is.
A simple routine that works
- Take levothyroxine on waking with water, on an empty stomach.
- Wait before breakfast and coffee as your leaflet or prescriber directs (the NHS says 30 to 60 minutes).
- Take mushroom capsules or powders later, with lunch or an evening meal.
- Keep calcium, iron and mineral-heavy blends well away from the tablet; your pharmacist may suggest a longer gap for these.
- Keep the routine consistent, so any change in your blood results can be interpreted.
Our medication interactions guide covers the other documented mushroom–drug concerns.
Can Supplements Distort Your Thyroid Blood Tests?
Yes, and the culprit usually isn't the mushroom. It's biotin (vitamin B7), which many labs use as part of their testing chemistry. Li and colleagues gave six healthy adults 10 mg of biotin a day for seven days, a dose common in over-the-counter supplements, and then ran 37 immunoassays on four diagnostic systems. The analytes tested included TSH, total and free T4, and total and free T3.
Interference appeared in 9 of the 23 assays that used biotin and streptavidin components, and in none of the 14 that didn't. The direction depended on assay design: 5 of 8 competitive assays read falsely high, and 4 of 15 sandwich assays read falsely low. A thyroid panel that's wrong in both directions at once can look like a thyroid problem that doesn't exist, or hide one that does.
Where do mushrooms come in? "Hair, skin and nails" and beauty blends often combine snow mushroom (Tremella) or other mushroom extracts with high-dose biotin. The NHS levothyroxine page lists biotin specifically because it can affect thyroid tests. If you take any biotin-containing product, tell the person ordering your blood test and ask whether you should pause it beforehand. Our guide to reading a supplement label shows where to find it on the ingredients list.
Do Mushrooms Contain Iodine?
Not in any amount that matters, and none is sold as an iodine source. That's the key difference from sea moss, which does carry iodine and is often marketed for the thyroid. Iodine is unusual among nutrients because too much can push the thyroid in either direction, and the people most at risk are those with existing thyroid disease.
The complication is blends. A "thyroid" or "wellness" product that combines mushrooms with sea moss, bladderwrack or kelp brings iodine along, often in undeclared and variable amounts. Our articles on sea moss and iodine safety and sea moss and thyroid basics explain why a bladderwrack-containing blend can carry far more iodine than sea moss alone. If you're on thyroid medication, read the full ingredients list, not just the front of the pack.
What If You Have Hashimoto's or Graves' Disease?
Then the question is immune modulation, and the honest answer is that nobody has tested it. Mushroom polysaccharides are marketed as immune "modulators", and some lab studies show them activating immune cells. Whether that's harmless, helpful or unhelpful in an autoimmune thyroid condition is unknown, because no trial has looked. Our autoimmune conditions article goes through what "immunomodulation" does and doesn't mean.
Two practical points follow. Tell your endocrinologist about any supplement you start, so an unexpected shift in antibodies or hormone levels can be interpreted. And watch the other ingredients in "adaptogen" blends: our review of ashwagandha side effects notes that ashwagandha isn't thyroid-neutral, with measurable T4 increases in a controlled study and published case reports of thyrotoxicosis. Mushroom blends that include it deserve extra care.
What Should You Actually Do?
| Issue | What the evidence says | What to do |
|---|---|---|
| Thyroid function | No human trial of any medicinal mushroom | Ignore "thyroid support" claims on mushroom products |
| Selenium | Most edible mushrooms under 1 µg/g dry weight | Don't rely on mushrooms for selenium; discuss selenium with your doctor |
| Levothyroxine absorption | Coffee, soy, calcium and iron reduce it; separation avoids it | Tablet first on an empty stomach; mushrooms and mushroom coffee later |
| Blood tests | High-dose biotin skews many biotin-based assays | Check blends for biotin; tell whoever orders your test |
| Iodine | Mushrooms aren't a source; sea moss and seaweed blends are | Read the full ingredient list of any blend |
| Autoimmune thyroid | Immune effects untested in Hashimoto's or Graves' | Tell your endocrinologist before starting anything |
None of this means people with thyroid conditions can't take mushroom supplements. It means the tablet comes first, the timing stays consistent, and the label gets read in full.
Frequently Asked Questions
Can mushrooms help an underactive thyroid?
There's no evidence that they can. No human trial has tested reishi, lion's mane, cordyceps, chaga or any other medicinal mushroom for thyroid function. Most edible mushrooms are also low in selenium, under 1 µg per gram of dry weight in Falandysz's review of 190 species. Levothyroxine, prescribed and monitored, remains the treatment for hypothyroidism.
Can I take mushroom supplements with levothyroxine?
There's no known direct interaction, but keep them apart. The NHS advises taking levothyroxine on an empty stomach, 30 to 60 minutes before food, caffeinated drinks or other medicines. A simple approach is the tablet on waking and mushroom capsules with lunch or dinner. Ask your pharmacist about any mineral-containing blend.
Does mushroom coffee affect thyroid medication?
The coffee part can. Skelin's 2017 review found coffee was among the factors with the greatest impact on reducing levothyroxine absorption. The mushroom content hasn't been studied. Drink mushroom coffee only after the gap your prescriber recommends for ordinary coffee, rather than alongside your tablet.
Can supplements affect thyroid blood test results?
Yes. In a 2017 JAMA study, 10 mg a day of biotin for a week interfered with 9 of 23 biotin-based lab assays, producing falsely high or falsely low results. Beauty blends often pair mushrooms with high-dose biotin, so check the label and tell whoever orders your test.
Are mushroom supplements safe with Hashimoto's?
It's unknown. No trial has studied any medicinal mushroom in Hashimoto's thyroiditis, and their immune effects have only been examined in lab and animal models. That's neither a green light nor a proven risk. Tell your endocrinologist before starting, and avoid blends that add ashwagandha or iodine-rich seaweed.
Related Articles
- Mushroom Supplements and Medication Interactions
- Mushrooms and Autoimmune Conditions
- Sea Moss and Iodine: How Much Is Too Much
- Sea Moss: Thyroid Support Guide
- Ashwagandha Side Effects and Liver Safety
- How to Read a Mushroom Supplement Label
Sources
- Falandysz J. Selenium in edible mushrooms. J Environ Sci Health C Environ Carcinog Ecotoxicol Rev. 2008;26(3):256-299. PubMed 18781538
- Wichman J, Winther KH, Bonnema SJ, Hegedüs L. Selenium Supplementation Significantly Reduces Thyroid Autoantibody Levels in Patients with Chronic Autoimmune Thyroiditis: A Systematic Review and Meta-Analysis. Thyroid. 2016;26(12):1681-1692. PubMed 27702392
- Skelin M, Lucijanić T, Amidžić Klarić D, Rešić A, Bakula M, Liberati-Čizmek AM, et al. Factors Affecting Gastrointestinal Absorption of Levothyroxine: A Review. Clin Ther. 2017;39(2):378-403. PubMed 28153426
- Li D, Radulescu A, Shrestha RT, Root M, Karger AB, Killeen AA, et al. Association of Biotin Ingestion With Performance of Hormone and Nonhormone Assays in Healthy Adults. JAMA. 2017;318(12):1150-1160. PubMed 28973622
- NHS. Levothyroxine: a medicine for an underactive thyroid (hypothyroidism). nhs.uk