Drug & supplement interaction

Iodine + Carbimazole

Carbimazole brand name: Neo-Mercazole.

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

Iodine has a moderate interaction with Carbimazole. Iodine might alter the effects of antithyroid drugs.

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

Iodine and Carbimazole

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

Moderate

ANTITHYROID DRUGS

Why this applies to Carbimazole

Carbimazole falls under ANTITHYROID DRUGS — the group Iodine interacts with.

Iodine might alter the effects of antithyroid drugs.
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.
Severity Moderate Likelihood Probable Evidence D

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..

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

Here is the thing to keep in mind: carbimazole works by telling your overactive thyroid to make less hormone. Iodine is the raw material your thyroid uses to build that hormone in the first place. So adding extra iodine can sort of work against what carbimazole is trying to do, especially at high supplement doses. That could make your treatment less reliable and let symptoms like a fast heartbeat, shakiness, or feeling overheated creep back.

To be fair, this is based on how these two behave in theory, not on strong studies, and the usual iodine you get from food or iodized salt is unlikely to be a problem. Concentrated iodine supplements (like kelp pills) are the real concern. Don't stop either one on your own, just check with your doctor or pharmacist first.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Goodman GA, Rall TW, Nies AS, Taylor P. The Pharmacological Basis of Therapeutics, 9th ed.
  2. 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.

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

Iodine Also Interacts With Other Medications

Iodine has 6 moderate known drug interactions in our database — the Carbimazole one above is one of them. If you take anything else, check it against the full list below.

Moderate 6 No known interaction 2,824 (incl. Carbimazole)
Taking anything else?

Check Another of Your Medications Against Iodine

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

Everything else you take

See Every Supplement That Interacts With Carbimazole

This page covers Iodine only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Carbimazole 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 Carbimazole page

“Carbimazole (Neo-Mercazole) calms an overactive thyroid, and since the drug itself can occasionally stress the liver, most of the supplements on this list earn their place by carrying liver toxicity of their own. Doubling up on liver stressors is the risk I take most seriously here, and the major-rated entries deserve a careful read fi…”

Reviewed by 2 · Jul 18, 2026

Open the Carbimazole interaction page

One more smart check

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 Carbimazole 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:

How much people look this up

Where Iodine and Carbimazole 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 Iodine
Top 5%

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

29 days ago today
Medication Carbimazole
Steady interest

#2,325 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 Iodine

What is Iodine?

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.

Read the full Iodine monograph & all interactions
Keep checking

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.

0Major
6Moderate
0Minor
2,823No known interaction
6 Moderate 2,823 No interaction
Moderate

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.

Showing the 60 most looked-up of 2,823 medications checked with no known interaction — see the full Iodine list.

See the full Iodine interactions page
See every supplement checked against Carbimazole, 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
Iodine monograph › Uses, safety, and every drug interaction in one place Carbimazole supplement interactions › Every supplement checked against Carbimazole, 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 Iodine and Carbimazole Together: Common Questions

Can you take Iodine with Carbimazole?
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 Iodine and Carbimazole 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 Carbimazole and Iodine?

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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.