Iodine + Methimazole
Methimazole brand name: Tapazole.
Iodine has a moderate interaction with Methimazole. Iodine might alter the effects of antithyroid drugs.
Read the full interaction reportIodine and Methimazole
Here is the interaction we found between these two, with the evidence behind it.
ANTITHYROID DRUGS
Why this applies to Methimazole
Methimazole falls under ANTITHYROID DRUGS — the group Iodine interacts with.
Iodine in high doses has been reported to cause both hyperthyroidism and hypothyroidism, depending on the individual's past medical history. Taking iodine while using antithyroid drugs could alter the effects of the antithyroid drugs.
Interaction 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..
Here's the thing to keep in mind: methimazole works by telling your thyroid to slow down and make less hormone. Iodine does almost the opposite job, since your thyroid uses iodine as a raw ingredient to build thyroid hormone in the first place. So adding extra iodine on top of methimazole can work against what your medication is trying to do, and it may make your hyperthyroidism harder to control.
This concern is based on how these two work in the body rather than strong clinical studies, so think of it as a reasonable caution, not a guarantee. The amount of iodine in regular food and iodized salt is usually fine. It's the concentrated supplements (like kelp pills or high-dose drops) that are more likely to throw things off. Before adding any iodine product, check with your doctor or pharmacist first.
- Goodman GA, Rall TW, Nies AS, Taylor P. The Pharmacological Basis of Therapeutics, 9th ed.
- Sterling JB, Heymann WR. Potassium iodide in dermatology: a 19th century drug for the 21st century-uses, pharmacology, adverse effects, and contraindications. J Am Acad Dermatol 2000;43:691-7. PubMed
What These Ratings Mean
Every interaction above is graded three ways — here’s the key to each label.
Clinically significant. Avoid the combination, or use only under close professional supervision.
Usually worth avoiding or managing — may need monitoring, a dose change, or timing apart.
Generally not serious. Be aware of it and mention it to your pharmacist.
- 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.
- 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.
Iodine Also Interacts With Other Medications
Iodine has 6 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.
Check Another of Your Medications Against Iodine
We haven’t checked that one against Iodine yet — ask our pharmacists directly.
Covers the 2,830 medications we’ve checked against Iodine. Pick one to open its full report.
See Every Supplement That Interacts With Methimazole
This page covers Iodine 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
Taking Iodine as Part of a Dietary Supplement Product? Check It for Interactions
We hold 14,226 real supplement products containing Iodine, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Iodine. Your product may carry other ingredients that interact with Methimazole too, on top of Iodine — and those would not show on this page. Find your product and we’ll check every ingredient on its label:
Where Iodine 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.
#19 of 1,452 supplements looked up here in the last 7 days
#1,323 of 2,830 medications looked up here in the last 7 days
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.
About Iodine
What is Iodine?
- Preventing iodine deficiency
- Supporting thyroid hormone production
- General energy and metabolism support
- Cognitive function
- Radiation emergency thyroid protection
Iodine is an essential mineral your body needs to make thyroid hormones, and most people get enough from iodized salt, dairy, and seafood. Supplements help when you are truly deficient, but taking too much can harm the thyroid, so high-dose products should only be used under medical supervision.
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.
Other Drugs & Iodine
Browse every other medication we’ve checked against Iodine — both the ones with a known interaction and the ones without. Select any drug for the full detail.
No drugs match “”.
6 interactions
No interaction 2,823 drugs checked — show the list
We also checked Iodine against these medications and found no known interaction in our sources. Open any page to confirm.
- Apixaban ›
- Levothyroxine ›
- Amlodipine ›
- Methylphenidate ›
- Warfarin ›
- Sertraline ›
- Testosterone ›
- Losartan Potassium ›
- Metoprolol ›
- Aspirin ›
- Ivermectin ›
- Rivaroxaban ›
- Rosuvastatin ›
- Escitalopram ›
- Tadalafil ›
- Acetaminophen ›
- Clopidogrel ›
- Valacyclovir ›
- Atorvastatin ›
- Docusate ›
- Hydroxyurea ›
- Abemaciclib ›
- Methamphetamine ›
- Sumatriptan ›
- Ibuprofen ›
- Semaglutide ›
- Tirzepatide ›
- Warfarin Sodium ›
- Prednisone ›
- Propranolol ›
- Lisdexamfetamine ›
- Acyclovir ›
- Bupropion ›
- Metformin ›
- Amoxicillin ›
- Lisinopril ›
- Bendamustine ›
- Amitriptyline ›
- Doxycycline ›
- Lamotrigine ›
- Fluoxetine ›
- Methotrexate ›
- Acetaminophen, Codeine ›
- Gabapentin ›
- Amphetamine ›
- Pregabalin ›
- Isotretinoin ›
- Dextroamphetamine ›
- Azithromycin ›
- Clonazepam ›
- Quetiapine ›
- Omeprazole ›
- Amlodipine Besylate ›
- Methylene Blue ›
- Duloxetine ›
- Letrozole ›
- Buspirone ›
- Citalopram ›
- Ciprofloxacin ›
- Naproxen ›
Showing the 60 most looked-up of 2,823 medications checked with no known interaction — see the full Iodine list.
Sources & How We Checked
Interaction details are evidence-graded and sourced from the Natural Medicines database. The medication overview comes from MedlinePlus.
- Natural Medicines (Therapeutic Research Center) — Evidence-graded clinical reference for vitamins, herbs and supplements — the basis for our interaction data.
- MedlinePlus, U.S. National Library of Medicine — NIH consumer drug information, used for the medication overviews.
- NIH Dietary Supplement Label Database (DSLD) — Official supplement product labels.
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
Taking Iodine and Methimazole Together: Common Questions
Can you take Iodine with Methimazole?
How serious is the Iodine and Methimazole interaction?
Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy
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