Drug & supplement interaction

Fulvic Acid + Thyroid Hormone

Thyroid Hormone brand name: Etwon.

Moderate Interaction
Medically reviewed by · Updated September 2026
The bottom line Moderate

Fulvic Acid has a moderate interaction with Thyroid Hormone. Theoretically, taking fulvic acid with thyroid hormone therapy might interfere with the ability to normalize thyroid function.

Read the full interaction report
SeverityModerate
LikelihoodPossible
EvidenceD
What do Severity, Likelihood & Evidence mean?
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Interaction report

Fulvic Acid and Thyroid Hormone

Here is the interaction we found between these two, with the evidence behind it.

Moderate

THYROID HORMONE

Theoretically, taking fulvic acid with thyroid hormone therapy might interfere with the ability to normalize thyroid function.
Animal research shows that fulvic acid increases the plasma level of thyroid-stimulating hormone (TSH) and decreases the thyroxine (T4):triiodothyronine (T3) ratio.
Severity Moderate Likelihood Possible Evidence D

Interaction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the practical takeaway if you take a thyroid medication like levothyroxine (Etwon) along with fulvic acid. The concern is that fulvic acid might throw off how well your thyroid levels stay balanced. In animal studies, fulvic acid nudged TSH up and shifted the T4-to-T3 ratio, which could mean your medication isn't keeping your thyroid where it should be.

If that happened, you might notice signs your dose feels off, such as fatigue, weight changes, feeling cold, or a racing heart. I want to be honest though: this is based only on lab and animal research, so it's more of a theoretical caution than a proven problem. Thyroid hormone is a sensitive medication where small shifts matter, so please check with your pharmacist or doctor before adding fulvic acid rather than changing anything on your own.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Vucskits, AV, Hullar, I, Bersenyi, A, Andrasofszky, E, Kulcsar, M, Szabo, J. Effect of fulvic and humic acids on performance, immune response and thyroid function in rats. J Anim Physiol Anim Nutr (Berl) 2010;94(6):721-728. PubMed

What These Ratings Mean

Every interaction above is graded three ways — here’s the key to each label.

Severity how clinically significant the interaction is
Major

Clinically significant. Avoid the combination, or use only under close professional supervision.

Moderate

Usually worth avoiding or managing — may need monitoring, a dose change, or timing apart.

Minor

Generally not serious. Be aware of it and mention it to your pharmacist.

Likelihood how strong the evidence is that the interaction actually happens in people
  • LikelyWell-controlled human studies have demonstrated the likely existence of this interaction.
  • ProbableInteraction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
  • PossibleInteraction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.
  • UnlikelyInteraction has been demonstrated in animal or in lab research but has been shown not to occur in humans.
Evidence the quality of the studies behind the rating (graded A–D)
  • AHigh-quality meta-analysis (quantitative systematic review).
  • BCase-control study.
  • CConsensus.
  • DAnecdotal evidence.

These ratings are for information only. Never start, stop, or otherwise change your therapy before speaking with your provider.

Keep it in perspective

Fulvic Acid Also Interacts With Other Medications

Fulvic Acid has 256 moderate known drug interactions in our database — the Thyroid Hormone one above is one of them. If you take anything else, check it against the full list below.

Moderate 256 No known interaction 2,574 (incl. Thyroid Hormone)
Taking anything else?

Check Another of Your Medications Against Fulvic Acid

Covers the 2,830 medications we’ve checked against Fulvic Acid. Pick one to open its full report.

Everything else you take

See Every Supplement That Interacts With Thyroid Hormone

This page covers Fulvic Acid only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Thyroid Hormone page lists 38 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Tiratricol (major), Acetyl-l-carnitine (moderate), Alpha-lipoic Acid (moderate) and Ascophyllum Nodosum (moderate).

By severity: 2 major · 26 moderate · 10 minor.

From our pharmacist’s overview on the Thyroid Hormone page

“The riskiest pairing on this page is tiratricol, which is itself a thyroid compound, so taking it alongside thyroid hormone (Etwon) stacks two doses of the same signal. It shares the list's only two major ratings with activated charcoal, which soaks up medication in the gut before the body can absorb it.”

Reviewed by 2 · Jul 18, 2026

Open the Thyroid Hormone interaction page

One more smart check

Taking Fulvic Acid as Part of a Dietary Supplement Product? Check It for Interactions

We hold 294 real supplement products containing Fulvic Acid, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Fulvic Acid. Your product may carry other ingredients that interact with Thyroid Hormone too, on top of Fulvic Acid — and those would not show on this page. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Fulvic Acid and Thyroid Hormone Sit Against Everything Else

Out of every supplement and medication people look up on HelloPharmacist, here is where these two land this week — and which way each has been moving.

Supplement Fulvic Acid
Top half

#467 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Thyroid Hormone
Top 10%

#181 of 2,830 medications looked up here in the last 7 days

29 days ago today

Position among everything looked up on this site, not a measure of how commonly either one is used or how important it is. A supplement can climb this list because of a news story. It counts every request to the page, automated ones included, and nothing here identifies anyone.

Supplement

About Fulvic Acid

What is Fulvic Acid?

  • General wellness and energy
  • Gut health
  • Antioxidant support
  • Mineral and nutrient supplementation
  • Immune support

Fulvic acid is a natural compound formed when plants and microbes break down in soil, and it is sold as a supplement for energy, gut, and overall wellness. Human research is very limited, so most claims are unproven. Talk with your pharmacist or doctor before using it, and avoid it during pregnancy and breastfeeding due to a lack of safety data.

Read the full Fulvic Acid monograph & all interactions
Keep checking

Other Drugs & Fulvic Acid

Browse every other medication we’ve checked against Fulvic Acid — both the ones with a known interaction and the ones without. Select any drug for the full detail.

0Major
256Moderate
0Minor
2,573No known interaction
256 Moderate 2,573 No interaction
Moderate

256 interactions

Showing 60 of 256 moderate interactions — see all 256 on the Fulvic Acid page.

No interaction 2,573 drugs checked — show the list

We also checked Fulvic Acid against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 2,573 medications checked with no known interaction — see the full Fulvic Acid list.

See the full Fulvic Acid interactions page
See every supplement checked against Thyroid Hormone, ranked by severity
Sources

Sources & How We Checked

Interaction details are evidence-graded and sourced from the Natural Medicines database. The medication overview comes from MedlinePlus.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

Parts of this content are provided by the Therapeutic Research Center, LLC.

DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.

© 2021 Therapeutic Research Center, LLC

Keep exploring
Fulvic Acid monograph › Uses, safety, and every drug interaction in one place Thyroid Hormone supplement interactions › Every supplement checked against Thyroid Hormone, ranked by severity Supplement interaction checker › Check any supplement or product against your medications Browse medications A–Z › Every drug we've checked against herbs & supplements Ask a pharmacist › Free, personal answer from our licensed team
Pharmacist Counseling Corner

Taking Fulvic Acid and Thyroid Hormone Together: Common Questions

Can you take Fulvic Acid with Thyroid Hormone?
There is a moderate interaction, so it may be acceptable with monitoring or timing changes — but check with your pharmacist first. Read the full details on this page and confirm with your pharmacist before combining them.
How serious is the Fulvic Acid and Thyroid Hormone interaction?
We rate it Moderate. This combination may require monitoring, a dose adjustment, or separating the times you take each one. Consult your pharmacist before using them together.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

Still Have a Question About Thyroid Hormone and Fulvic Acid?

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This information is for education only and is not a substitute for professional medical advice. Always check with your pharmacist or doctor before starting, stopping, or combining supplements and medications.