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Dietary supplement

Kelp 500 mg Ingredients & Drug Interactions

by Dr. Clark Store

Kelp 500 mg label
See full label image
Capsule Category: Non-nutrient/non-botanical
Most serious interaction: Moderate
Clinical methodology reviewed by · Updated Sep 16, 2026 · Label data from the NIH DSLD
What is this page for?

First and foremost: checking Kelp 500 mg against your medications. The heart of this page is the interaction checker and the full interaction report — how this product’s ingredients may interact with prescription and over-the-counter medicines you may be taking.

Around that, we add a pharmacist’s high-level view of the product as a whole — what’s inside, the evidence for its stated use, how transparent the label is, and what safety data exists — so you can see the full picture in one place. It’s educational information from our licensed clinical databases and the clinical staff at HelloPharmacist — not medical advice — and we don’t sell or endorse products. Our editorial policy

The interaction bottom line Most serious interaction: Moderate

Kelp 500 mg is a dietary supplement by Dr. Clark Store with 1 active ingredient. Its ingredients are commonly taken for thyroid support, iodine source, weight management.Based on those ingredients, 891 medications have a known interaction with it, the most serious rated moderate. The ingredients most likely to interact are Kelp. Use the checker below to test your specific medication, or read the full HelloPharmacist Interaction Report.

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Check Your Meds Against Kelp 500 mg by Dr. Clark Store

Ask about any prescription or over-the-counter medication and we check it for interactions with Kelp 500 mg by Dr. Clark Store — and tell you which ingredient is responsible.

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HelloPharmacist Scorecard of Kelp 500 mg by Dr. Clark Store

Our pharmacy team’s full take, with four database checks built into the cards below — a summary of what is known, not a grade of the product itself.

From our pharmacy team — supplement deep dive

Generated from HelloPharmacist’s pharmacist-curated databases and editorial rules · Last generated Jul 11, 2026

What’s inside

Full disclosure
Ingredient Transparency · database check
Full

Every active ingredient lists its own amount on the label.

Why this rating?
  • The label discloses an exact amount for 1 of its 1 active ingredient.
  • No proprietary blends here — you can verify the dose of every single component.

This product contains one active ingredient: kelp (Fucus vesiculosus), a seaweed, at 500 mg per capsule. The capsule itself is made from gelatin, which is an inactive ingredient.

Does it work?

Not established
Evidence for Intended Use · database check
By FDA rules, dietary supplements can’t claim to treat, cure, or prevent disease — so labels speak in careful marketing language. We discern each product’s intended use from its name, label claims, and label statements, then grade the clinical evidence for that use. How these ratings are computed
Not established

The graded evidence we hold for these ingredients covers different conditions than the ones this product is marketed for, so there's no established rating for its stated use — see Fucus Vesiculosus's own graded uses on its monograph.

Why this rating?
  • The label markets this product for: natural iodine source.
  • We looked for evidence on: Iodine deficiency, Hypothyroidism, Thyroid function, Iodine supplementation.
  • The closest evidence on file: Fucus Vesiculosus is rated "Insufficient Reliable Evidence To Rate" for Hypothyroidism (Natural Medicines).
  • Also on file: Fucus Vesiculosus is rated "Insufficient Reliable Evidence To Rate" for Iodine deficiency.

We don't have enough reliable evidence in our data to say whether kelp works for aging skin, heart disease, constipation, diarrhea, or indigestion. The ratings across these uses all show insufficient evidence — meaning the science just isn't established yet for any of them.

The evidence, ingredient by ingredient Fucus Vesiculosus

How safe is it?

Well-documented data
Safety Information · database check
Well characterized

Adverse-effect, pregnancy, and general safety data are on file for most of these ingredients.

Why this rating?
  • We hold adverse-effect (side-effect) data for 1 of the 1 matched ingredient.
  • Pregnancy & breastfeeding safety ratings cover 1 of 1.
  • General safety write-ups exist for 1 of 1.
  • Remember: this measures how much safety information exists. Thin data is not the same as being safe.

Kelp may be unsafe when you take it by mouth because of its variable and high iodine content, which can disrupt your thyroid. The plant can also concentrate heavy metals from the ocean, which is another concern.

If you're pregnant, the excess iodine and possible heavy metal content make it unsafe — the data advises against it. If you're breastfeeding, iodine passes into your breast milk and may affect your baby's thyroid, so the safety data advises against it too.

The most common adverse effects from taking kelp orally are goiter (enlarged thyroid), hyperthyroidism (overactive thyroid), and hypothyroidism (underactive thyroid). A rare serious effect is thyroid cancer.

One person developed heart palpitations and fainting after taking a weight loss supplement containing kelp and other herbs, with dangerous heart rhythm changes on ECG — though it's unclear whether kelp alone caused it.

Side effects, ingredient by ingredient Fucus Vesiculosus

Meds to double-check

Moderate interaction found
Known Interaction Concern · database check
Moderate identified

The most serious documented interaction for these ingredients is Moderate. Check your medications for a personalized result.

Why this rating?
  • 1 of the 1 matched ingredient can interact with medications — Fucus Vesiculosus.
  • The most serious interaction on file is rated Moderate.
  • Some involve high-stakes drug classes: anticoagulant / antiplatelet drugs; lithium.
  • For scale: 892 individual medications appear in the full list. A big number alone doesn't make a product dangerous — what matters is whether YOUR medication is on it, so run yours through the interaction checker on this page.

Before you take this, double-check with your pharmacist if you're on lithium, any antithyroid drug, thyroid hormone replacement, or amiodarone — these Moderate interactions can seriously affect how your thyroid works. Also mention if you take blood thinners or any heart, blood pressure, or mood medication, since Minor interactions are possible.

Check your own medication Run your meds through the checker above

The bottom line

Scorecard at a glanceFully disclosed formula with no established evidence rating for its marketed use. Moderate medication interactions have been identified, and safety information is well characterized.

Kelp is not a good fit if you take any thyroid medication, lithium, amiodarone, or blood thinners — talk with your pharmacist first. It's off limits in pregnancy and breastfeeding.

If you're considering it for another reason, know that we don't have solid evidence it works, and the iodine content carries real thyroid risk.

Educational only — not medical advice; always confirm with your pharmacist. Our editorial policy · How we use AI

Assessment coverage: 1 of 1 active ingredient matched to our full ingredient reviews (monographs). Based on the product label dated May 22, 2020.

This Scorecard evaluates available label information, ingredient evidence, and known medication-safety considerations. It does not independently verify product identity, purity, potency, contamination, or manufacturing quality. How these ratings are computed

At a glance

General information

Key facts about Kelp 500 mg, straight from the product label.

Brand Dr. Clark Store
Barcode (UPC) 652384106757
Net contents 100 Capsule(s)
Market status On market
Date entered into DSLD May 22, 2020
DSLD ID 219971
Product type Non-nutrient/non-botanical
Supplement form Capsule
Dietary claims / uses Nutrient, All Other, Structure/Function
Intended target group(s) Adult (18 - 50 Years)
From the label
Everything in this section is reproduced from the manufacturer’s own product label — it’s the label speaking, not HelloPharmacist. We show it so you can see exactly what the maker states; we don’t verify or endorse those statements.

Supplement Facts

The label details for Kelp 500 mg by Dr. Clark Store, sourced from the NIH Dietary Supplement Label Database.

Supplement Facts

Daily Value (DV) Target Group(s):
Adults and children 4 or more years of age
Minimum serving Sizes:
1 Capsule(s)
Maximum serving Sizes:
1 Capsule(s)
Servings per container
100
UPC/BARCODE
652384106757
IngredientAmount% DV
Kelp500 mg--

Other ingredients: Gelatin Capsules

Tap any ingredient to jump to its full detail below.

Label statements
These statements are the manufacturer’s wording, reproduced from the product label — the label is saying it, not HelloPharmacist. We don’t verify or endorse them.
Suggested/Recommended/Usage/Directions

Suggested Use: Take 1 capsule, preferably with a meal, or as directed by a healthcare professional.

General Statements

Self Health Resource Center 1055 Bay Blvd., Ste A Chula Vista, CA 91911 Customer Service Toll Free: (866) DR-CLARK (372-5275) www.DrClarkStore.com

Leader in purity Established by Dr. Clark's family in 1993

Company does not adopt any Dr. Clark claims.

Formulation

Our products don't contain flow agents like magnesium stearate. Not now, not ever.

Seals/Symbols

Made in USA

GMP Quality Assured

Formula

Natural iodine source

FDA Statement of Identity

Dietary Supplement

Storage

Store at room temperature.

Precautions

Keep away from children.

Warning: If you are pregnant, nursing or taking any medications, consult your doctor before use.

If any adverse reactions occur, immediately stop using this product and consult your doctor. If seal under cap is damaged or missing, do not use.

FDA Disclaimer Statement

These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure or prevent any disease.

Is this label outdated? Report a formula or label change and our pharmacy team will review it.

See for yourself

Kelp 500 mg by Dr. Clark Store label

The label scan from the NIH Dietary Supplement Label Database. Tap to enlarge.

Kelp 500 mg label

Label images are published by the NIH Dietary Supplement Label Database for the version of this product on file. Always read your actual product label.

View the full label (PDF)
What’s inside

The Ingredients in Kelp 500 mg by Dr. Clark Store

This is the 1 active ingredient this product is made of. Select it to open its full monograph.

Serving size1 Capsule(s) Dosage formCapsule Servings per container100 Amounts shown are per serving.

Kelp

Interacts with
891 drugs
500 mg per serving

Fucus vesiculosus (bladderwrack) is a brown seaweed rich in iodine that has been used traditionally for thyroid concerns, weight, and skin. There is l...

Kelp monograph & interactions

Other (inactive) ingredients: Gelatin Capsules. These complete the product’s ingredient list but are not active constituents.

Interaction report

Kelp 500 mg by Dr. Clark Store Drug Interactions

Want to check YOUR meds against Kelp 500 mg?

Ask about interactions with your drugs in plain English — “Can I take it with lisinopril?” — and we find you the answer in seconds, ingredient by ingredient.

 Go to the checker
891Drugs
23 Moderate 868 Minor

Ingredients driving the most interactions

Kelp 891

Individual Drug Interactions

The ingredients in Kelp 500 mg interact with 891 drugs. Click any drug to see the details.

1 of the 1 ingredient in Kelp 500 mg interact with drugs. Each result below shows which ingredient is responsible. Kelp

Each ingredient & the kinds of drugs it affects

For each ingredient in Kelp 500 mg with known interactions, here are the types of medications it can affect. Open any type for the detail — or search your exact drug in the checker above.

Kelp9 drug types · 891 drugs

Amiodarone (Cordarone)

Theoretically, combining Fucus vesiculosus with amiodarone might cause excessively high iodine levels.
Fucus vesiculosus contains high concentrations of iodine. Amiodarone contains 37.3% iodine and can increase iodine levels. Concomitant use might increase the risk of having excessive iodine levels and adversely affecting thyroid function. Monitor thyroid function.

Likelihood Probable Evidence D
Antithyroid Drugs

Due to its iodine content, Fucus vesiculosus might alter the effects of antithyroid drugs.
Fucus vesiculosus contains high concentrations of iodine. Iodine in high doses has been reported to cause both hyperthyroidism and hypothyroidism, depending on the individual's past medical history. Taking Fucus vesiculosus while using antithyroid drugs could alter the effects of the antithyroid drugs.

Likelihood Possible Evidence D
Lithium

Concomitant use of Fucus vesiculosus and lithium has resulted in hyperthyroidism.
There is a case of hyperthyroidism occurring in a patient taking Fucus vesiculosus and lithium. Monitor thyroid hormones closely in patients taking lithium and Fucus vesiculosus concomitantly.

Likelihood Possible Evidence D
Thyroid Hormone

Due to its iodine content, Fucus vesiculosus might alter the effects of thyroid hormone.
Fucus vesiculosus contains high concentrations of iodine. Iodine in high doses has been reported to cause both hyperthyroidism and hypothyroidism, depending on the individual's past medical history. Taking Fucus vesiculosus while using thyroid hormone could alter the effects of thyroid hormone.

Likelihood Possible Evidence D
Anticoagulant/Antiplatelet Drugs

Theoretically, taking Fucus vesiculosus with antiplatelet or anticoagulant drugs might increase the risk of bruising and bleeding.
In vitro evidence suggests that a constituent of Fucus vesiculosus, known as fucoidan, has anticoagulant effects. However, in clinical research, fucoidan does not seem to have significant anticoagulant activity when taken orally, possibly due to poor absorption.

Likelihood Unlikely Evidence D
Cytochrome P450 2C8 (Cyp2C8) Substrates

Theoretically, concomitant use of Fucus vesiculosus with CYP2C8 substrates might increase the risk for adverse effects.
In vitro research shows that fucoidan, a constituent of Fucus vesiculosus, inhibits CYP2C8. This interaction has not been reported in humans.

Likelihood Possible Evidence D
Cytochrome P450 2C9 (Cyp2C9) Substrates

Theoretically, concomitant use of Fucus vesiculosus with CYP2C9 substrates might increase the risk for adverse effects.
In vitro research shows that fucoidan, a constituent of Fucus vesiculosus, inhibits CYP2C9. This interaction has not been reported in humans.

Likelihood Possible Evidence D
Cytochrome P450 2D6 (Cyp2D6) Substrates

Theoretically, concomitant use of Fucus vesiculosus with CYP2D6 substrates might alter the effects of these substrates.
In vitro research shows that fucoidan, a constituent of Fucus vesiculosus, both inhibits and induces CYP2D6. This interaction has not been reported in humans.

Likelihood Possible Evidence D
Cytochrome P450 3A4 (Cyp3A4) Substrates

Theoretically, concomitant use of Fucus vesiculosus with CYP3A4 substrates might increase the risk for adverse effects.
In vitro research shows that fucoidan, a constituent of Fucus vesiculosus, inhibits CYP3A4. This interaction has not been reported in humans.

Likelihood Possible Evidence D
Kelp full monograph & interactions
The maker

Brand information

Manufacturer and brand details for Kelp 500 mg, from the product label.

Dr. Clark Store

See all Dr. Clark Store products
Name
Dr. Clark Store
Street Address
1055 Bay Blvd., Ste A
City
Chula Vista
State
CA
ZipCode
91911
Phone Number
(866) 372-5275
Web Address
www.DrClarkStore.com
Pharmacist Counseling Corner

Kelp 500 mg by Dr. Clark Store: Common Questions

Does Kelp 500 mg by Dr. Clark Store interact with any medications?
Yes. Based on its ingredients, Kelp 500 mg has a known interaction with 891 medications. Use the checker to see how it interacts with a specific drug.
How can one product interact with so many drugs?
Kelp 500 mg contains a single active ingredient, and that one ingredient can interact with many different medications on its own. We check it against each medication and show the mechanism responsible.
Where does this information come from?
The product label data comes from the NIH Dietary Supplement Label Database (DSLD); the interaction data is built on the Natural Medicines database and reviewed by HelloPharmacist pharmacists.
Can I take kelp if I'm pregnant or breastfeeding?
No — the safety data advises against it in both cases. During pregnancy, the excess iodine and possible heavy metal content are unsafe. Iodine passes into breast milk and may affect your baby's thyroid. Talk with your doctor before taking it.
What are the side effects of kelp?
The most common effects from taking it by mouth are goiter (an enlarged thyroid), hyperthyroidism, and hypothyroidism — all related to its high iodine content. Rarely, thyroid cancer has been reported. One person also developed heart palpitations, fainting, and dangerous heart rhythm changes, though it's unclear if kelp alone was responsible.
Does kelp actually work for anything?
We don't have enough reliable evidence in our data to say whether it works for aging skin, heart disease, constipation, diarrhea, or indigestion. The science just isn't established yet.
Why is kelp risky for the thyroid?
Kelp is packed with iodine, which your thyroid needs — but too much can disrupt it in either direction, causing overactivity or underactivity. The risk is even higher if you're already taking thyroid medication, lithium, or amiodarone.
Can kelp make me bleed more easily?
There's a theoretical risk if you take blood thinners, since a compound in kelp called fucoidan has anticoagulant properties in the lab. However, this hasn't been seen in actual people yet. Still, mention it to your pharmacist if you're on blood thinners.

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

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Label information is sourced from the NIH Dietary Supplement Label Database and reflects the product version on file; always read your actual product label. This page is for education only and is not a substitute for professional medical advice. Confirm with your pharmacist or doctor before combining supplements and medications.

Kelp 500 mg label
Go deeper

The Full Monographs Behind Kelp 500 mg’s Ingredients

Every ingredient we hold a full HelloPharmacist monograph for — uses, evidence, safety, and the complete interaction list.

Herb & supplement monograph

Fucus Vesiculosus

Interacts with 891 drugs

Fucus vesiculosus (bladderwrack) is a brown seaweed rich in iodine that has been used traditionally for thyroid concerns, weight, and skin. There is little solid human evidence to support mo...

Read the full Fucus Vesiculosus monograph →
Sources

Sources & How We Checked

Kelp 500 mg's label data comes from the NIH Dietary Supplement Label Database; the ingredient interaction data is from the Natural Medicines database, reviewed by our pharmacists.

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

The 15 references behind this product’s interaction data

Every citation that drives the interaction findings for this product’s ingredients, from the evidence-graded Natural Medicines (TRC Healthcare) database. Open an ingredient to browse its citations — links open the study on PubMed or the publisher’s site.

Fucus Vesiculosus 15 references
  1. Goodman GA, Rall TW, Nies AS, Taylor P. The Pharmacological Basis of Therapeutics, 9th ed.
  2. Food and Nutrition Board, Institute of Medicine. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. Washington, DC: National Academy Press, 2002.
  3. Phaneuf D, Cote I, Dumas P, et al. Evaluation of the contamination of marine algae (Seaweed) from the St. Lawrence River and likely to be consumed by humans. Environ Res 1999;80:S175-S182. PubMed
  4. Durig J, Bruhn T, Zurborn KH, et al. Anticoagulant fucoidan fractions from Fucus vesiculosus induce platelet activation in vitro. Thromb Res 1997;85:479-91. PubMed
  5. Conz PA, La Greca G, Benedetti P, et al. Fucus vesiculosus: a nephrotoxic alga? Nephrol Dial Transplant 1998;13:526-7.
  6. Ohye H, Fukata S, Kanoh M, et al. Thyrotoxicosis caused by weight-reducing herbal medicines. Arch Intern Med 2005;165:831-4. PubMed
  7. Okamura K, Inoue K, Omae T. A case of Hashimoto's thyroiditis with thyroid immunological abnormality manifested after habitual ingestion of seaweed. Acta Endocrinol (Copenh) 1978;88:703-12. PubMed
  8. Agarwal SC, Crook JR, Pepper CB. Herbal remedies -- how safe are they? A case report of polymorphic ventricular tachycardia/ventricular fibrillation induced by herbal medication used for obesity. Int J Cardiol 2006;106:260-1. PubMed
  9. 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
  10. Catania, M. A., Oteri, A., Caiello, P., Russo, A., Salvo, F., Giustini, E. S., Caputi, A. P., and Polimeni, G. Hemorrhagic cystitis induced by an herbal mixture. South.Med.J. 2010;103(1):90-92. PubMed
  11. Cumashi, A., Ushakova, N. A., Preobrazhenskaya, M. E., D'Incecco, A., Piccoli, A., Totani, L., Tinari, N., Morozevich, G. E., Berman, A. E., Bilan, M. I., Usov, A. I., Ustyuzhanina, N. E., Grachev, A. A., Sanderson, C. J., Kelly, M., Rabinovich, G. A., I
  12. Irhimeh, M. R., Fitton, J. H., and Lowenthal, R. M. Pilot clinical study to evaluate the anticoagulant activity of fucoidan. Blood Coagul.Fibrinolysis 2009;20(7):607-610. PubMed
  13. Arbaizar, B. and Llorca, J. [Fucus vesiculosus induced hyperthyroidism in a patient undergoing concomitant treatment with lithium]. Actas Esp.Psiquiatr. 2011;39(6):401-403.
  14. Church FC, Meade JB, Treanor RE, and et al. Antithrombin activity of fucoidan. The interaction of fucoidan with heparin cofactor II, antithrombin III, and thrombin. J Biol Chem 2-25-1989;264(6):3618-3623. DOI
  15. Mathew L, Burney M, Gaikwad A, et al. Preclinical evaluation of safety of fucoidan extracts from Undaria pinnatifida and Fucus vesiculosus for use in cancer treatment. Integr Cancer Ther 2017;16(4):572-84.

See these in context on the Fucus Vesiculosus monograph →

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

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