Drug & supplement interaction

Sea Moss + Methimazole

Methimazole brand name: Tapazole.

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

Sea Moss has a moderate interaction with Methimazole. Due to its iodine content, sea moss might alter the effects of antithyroid drugs.

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

Sea Moss and Methimazole

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

Moderate

ANTITHYROID DRUGS

Why this applies to Methimazole

Methimazole falls under ANTITHYROID DRUGS — the group Sea Moss interacts with.

Due to its iodine content, sea moss might alter the effects of antithyroid drugs.
Sea moss contains approximately 4-7 mcg of iodine per gram. Iodine in high doses has been reported to cause both hyperthyroidism and hypothyroidism, depending on the individual's past medical history. Taking sea moss could theoretically alter the effects of antithyroid drugs.
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 thing to keep in mind: methimazole works by dialing down how much thyroid hormone your overactive thyroid pumps out. Sea moss naturally carries iodine, and iodine is the raw material your thyroid uses to make those hormones. So adding a concentrated, variable source of iodine while you're trying to calm the thyroid down can work against what your medication is doing, or in some people swing things the other way.

In real terms, this could mean your hyperthyroid symptoms come back or shift, things like a racing heart, jitteriness, weight changes, or feeling too hot or too cold. To be fair, this concern is theoretical and based on how iodine behaves, not strong studies. Still, with a thyroid condition I'd hold off and check with your doctor or pharmacist first.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Darias-Rosales J, Rubio C, Gutiérrez ÁJ, Paz S, Hardisson A. Risk assessment of iodine intake from the consumption of red seaweeds (Palmaria palmata and Chondrus crispus). Environ Sci Pollut Res Int 2020;27(36):45737-45741. 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

Sea Moss Also Interacts With Other Medications

Sea Moss has 21 moderate known drug interactions in our database — the Methimazole one above is one of them. If you take anything else, check it against the full list below.

Moderate 21 No known interaction 2,809 (incl. Methimazole)
Taking anything else?

Check Another of Your Medications Against Sea Moss

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

From our Q&A

Questions About Sea Moss or Methimazole

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Sea Moss or Methimazole, not necessarily both, but if one is close to what you were about to ask it will usually go further than a database entry can:

Not quite your question? Ask our pharmacists directly — it is free, there is no account required, and answers usually come back within 24 hours.

Everything else you take

See Every Supplement That Interacts With Methimazole

This page covers Sea Moss only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Methimazole page lists 64 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Beer (major), Siberian Cocklebur (major), Wine (major) and Ascophyllum Nodosum (moderate).

By severity: 4 major · 51 moderate · 9 minor.

From our pharmacist’s overview on the Methimazole page

“Methimazole (Tapazole) treats an overactive thyroid, and because the drug can stress the liver on its own, this list calls for real vigilance. Of the 64 supplements on file, 4 are rated major, with 51 moderate and 9 minor.”

Reviewed by 2 · Jul 18, 2026

Open the Methimazole interaction page

How much people look this up

Where Sea Moss and Methimazole 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 Sea Moss
Top half

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

29 days ago today
Medication Methimazole
Top half

#1,323 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 Sea Moss

What is Sea Moss?

Sea Moss
  • Source of iodine and minerals
  • Thyroid support
  • Respiratory issues and cough
  • Digestive support
  • Skin and hair health
  • General immune and antioxidant support

Sea moss is a type of red seaweed that is naturally rich in iodine and several minerals, and it is popular as a 'whole-food' supplement. Strong human evidence for most of its health claims is lacking, and its high and variable iodine content can be a real concern, especially for people with thyroid problems. Talk to your pharmacist or doctor before using it, particularly if you are pregnant, breastfeeding, or have a thyroid condition.

Read the full Sea Moss monograph & all interactions
Medication

About Methimazole

What Is Methimazole Used For?

Brand name: Tapazole

Methimazole tablets are used in adults and children with hyperthyroidism (an overactive thyroid) due to Graves' disease or toxic multinodular goiter when surgery or radioactive iodine is not the right option. They work to lower thyroid hormone levels and ease symptoms.

Methimazole tablets are also used to bring thyroid hormone levels down before a patient undergoes thyroidectomy (thyroid surgery) or radioactive iodine treatment, making those procedures safer.

See full Methimazole drug information
Keep checking

Other Drugs & Sea Moss

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

0Major
21Moderate
0Minor
2,808No known interaction
21 Moderate 2,808 No interaction
Moderate

21 interactions

No interaction 2,808 drugs checked — show the list

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

Showing the 60 most looked-up of 2,808 medications checked with no known interaction — see the full Sea Moss list.

See the full Sea Moss interactions page
See every supplement checked against Methimazole, 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
Sea Moss monograph › Uses, safety, and every drug interaction in one place Methimazole supplement interactions › Every supplement checked against Methimazole, ranked by severity Methimazole drug information › The full plain-English guide to this medication 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 Sea Moss and Methimazole Together: Common Questions

Can you take Sea Moss with Methimazole?
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 Sea Moss and Methimazole 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 Methimazole and Sea Moss?

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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.