Drug & supplement interaction

Dulse + Propylthiouracil, PTU

Propylthiouracil, PTU brand name: Propylthiouracil.

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

Dulse has a moderate interaction with Propylthiouracil, PTU. Theoretically, due to its iodine content, dulse 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

Dulse and Propylthiouracil, PTU

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

Moderate

ANTITHYROID DRUGS

Why this applies to Propylthiouracil, PTU

Propylthiouracil, PTU falls under ANTITHYROID DRUGS — the group Dulse interacts with.

Theoretically, due to its iodine content, dulse might alter the effects of antithyroid drugs.
Dulse is rich in iodine. Iodine in high doses has been reported to cause both hyperthyroidism and hypothyroidism, depending on the individual's past medical history.
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: you're taking propylthiouracil (PTU) to calm down an overactive thyroid by blocking how much thyroid hormone your gland makes. Dulse, a red seaweed, is naturally loaded with iodine, and iodine is the raw material your thyroid uses to build those very hormones. So adding a concentrated iodine source can work against what your medication is trying to do, and it may make your thyroid harder to control.

This is a theoretical concern based on how iodine behaves, not on strong studies, so don't panic. Eating dulse occasionally as a food is different from taking concentrated supplements day after day. Since your thyroid levels are already being carefully managed, please check with your pharmacist or doctor before using dulse supplements, and don't change your PTU on your own.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Allsopp P, Crowe W, Bahar B, et al. The effect of consuming Palmaria palmata-enriched bread on inflammatory markers, antioxidant status, lipid profile and thyroid function in a randomised placebo-controlled intervention trial in healthy adults. Eur J Nutr PubMed
  2. Takase T, Nakamura A, Miyoshi H, et al. Effects of Palmaria palmata on lipid metabolism and glycemic control in participants with hypercholesterolemia in a randomized double-blind placebo-controlled trial. Phytother Res. 2020.

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

Dulse Also Interacts With Other Medications

Dulse has 22 moderate, 62 minor known drug interactions in our database — the Propylthiouracil, PTU one above is one of them. If you take anything else, check it against the full list below.

Moderate 22 Minor 62 No known interaction 2,746 (incl. Propylthiouracil, PTU)
Taking anything else?

Check Another of Your Medications Against Dulse

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

From our Q&A

Questions About Dulse or Propylthiouracil, PTU

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Dulse or Propylthiouracil, PTU, 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 Propylthiouracil, PTU

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

Open the Propylthiouracil, PTU interaction page

One more smart check

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

We hold 546 real supplement products containing Dulse, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Dulse. Your product may carry other ingredients that interact with Propylthiouracil, PTU too, on top of Dulse — 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 Dulse and Propylthiouracil, PTU 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 Dulse
Top 25%

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

29 days ago today
Medication Propylthiouracil, PTU
Top half

#985 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 Dulse

What is Dulse?

Dulse
  • Nutritional supplement (iodine, minerals)
  • Source of plant protein
  • General wellness
  • Anti-inflammatory support
  • Thyroid/iodine support

Dulse is a red seaweed eaten as a food in many coastal cultures and is a natural source of iodine, potassium, protein, and antioxidant compounds. As a food it is generally considered safe for most people, but concentrated supplements can deliver large amounts of iodine and potassium, so use caution. Talk to your pharmacist or doctor before using it medicinally, especially if you have thyroid or kidney problems.

Read the full Dulse monograph & all interactions
Medication

About Propylthiouracil

What Is Propylthiouracil Used For?

Brand name: Propylthiouracil

Propylthiouracil tablets are used to treat hyperthyroidism — a condition where the thyroid gland makes too much thyroid hormone. It is specifically indicated for patients with Graves' disease or toxic multinodular goiter who cannot tolerate methimazole (another antithyroid drug) and for whom surgery or radioactive iodine is not a suitable option.

It is also used to bring thyroid hormone levels under control before a patient undergoes thyroidectomy (thyroid surgery) or radioactive iodine therapy, again in patients who cannot tolerate methimazole. Because of its serious liver risks, propylthiouracil is generally a second-choice treatment — used when other options are not appropriate.

See full Propylthiouracil drug information
Keep checking

Other Drugs & Dulse

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

0Major
22Moderate
62Minor
2,745No known interaction
22 Moderate 62 Minor 2,745 No interaction
Moderate

22 interactions

Minor

62 interactions

Showing 60 of 62 minor interactions — see all 62 on the Dulse page.

No interaction 2,745 drugs checked — show the list

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

Showing the 60 most looked-up of 2,745 medications checked with no known interaction — see the full Dulse list.

See the full Dulse interactions page
See every supplement checked against Propylthiouracil, PTU, 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
Dulse monograph › Uses, safety, and every drug interaction in one place Propylthiouracil, PTU supplement interactions › Every supplement checked against Propylthiouracil, PTU, ranked by severity Propylthiouracil 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 Dulse and Propylthiouracil, PTU Together: Common Questions

Can you take Dulse with Propylthiouracil, PTU?
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 Dulse and Propylthiouracil, PTU 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 Propylthiouracil, PTU and Dulse?

Our pharmacists answer your medication & supplement questions — free.

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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.