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Dietary supplement

Norwegian Kelp Ingredients & Drug Interactions

by Nature's Harmony

Norwegian Kelp label
See full label image
Capsule Category: Botanical With Nutrients
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 Norwegian Kelp 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

Norwegian Kelp is a dietary supplement by Nature's Harmony with 1 active ingredient. Its ingredients are commonly taken for source of dietary iodine, thyroid support, cervical dilation (medical procedure).Based on those ingredients, 70 medications have a known interaction with it, the most serious rated moderate. The ingredients most likely to interact are Norwegian Kelp (Laminaria digitata) powder. Use the checker below to test your specific medication, or read the full HelloPharmacist Interaction Report.

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Check Your Meds Against Norwegian Kelp by Nature's Harmony

Ask about any prescription or over-the-counter medication and we check it for interactions with Norwegian Kelp by Nature's Harmony — and tell you which ingredient is responsible.

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HelloPharmacist Scorecard of Norwegian Kelp by Nature's Harmony

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 Aug 27, 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.
  • “Norwegian Kelp (Laminaria digitata) powder” is listed as a grouped ingredient — the label gives one combined amount (97 mg) without saying how much of each component you get.

Norwegian Kelp by Nature's Harmony is a single-ingredient product: iodine, supplied as Norwegian kelp (Laminaria digitata) powder. The capsule itself is made from gelatin and contains inactive ingredients including cellulose, silicon dioxide, and magnesium stearate.

Does it work?

Strong evidence
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
Strong

Clinical evidence supports at least one of this product's ingredients for its stated purpose.

Why this rating?
  • The label markets this product for: source of iodine.
  • We looked for evidence on: Iodine deficiency, thyroid function, hypothyroidism, goiter.
  • The strongest evidence on file: Iodine is rated "Likely Effective" for Iodine deficiency (Natural Medicines).

Iodine in this form is likely effective for preventing radiation exposure to the thyroid and for treating iodine deficiency. It's possibly effective for oral mucositis (mouth sores) and periodontitis (gum disease), though the evidence for those uses is less established.

The evidence, ingredient by ingredient Laminaria Iodine

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.

Iodine is well tolerated at normal dietary levels, but high doses can cause thyroid problems, so stick to the amount on the label and your doctor's guidance. Some people experience abdominal upset, diarrhea, nausea, metallic taste, or headache.

Rarely, iodine can trigger a serious allergic reaction (anaphylaxis) or skin problems like acneform lesions if taken in very large amounts over time. In pregnancy, adequate iodine is important for your baby's development, but only take what your doctor advises — avoid high-dose products.

During breastfeeding, some iodine passes into breast milk, so follow your doctor's recommendation.

Side effects, ingredient by ingredient Laminaria Iodine

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 — Iodine.
  • The most serious interaction on file is rated Moderate.
  • Some involve high-stakes drug classes: lithium.
  • For scale: 7 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 Norwegian Kelp, check with your doctor or pharmacist if you're on lithium, antithyroid medications, or amiodarone — all three have Moderate interactions with iodine that require thyroid monitoring.

Check your own medication Run your meds through the checker above

The bottom line

Scorecard at a glanceFully disclosed formula with clinical evidence supporting its stated purpose. Moderate medication interactions have been identified, and safety information is well characterized.

Norwegian Kelp is useful if you need iodine for deficiency or thyroid protection after radiation exposure. If you take lithium, antithyroid drugs, or amiodarone, you'll need to check with your doctor or pharmacist before starting it — thyroid monitoring may be necessary.

Talk with your own healthcare provider about whether this product fits your situation.

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 24, 2013.

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 Norwegian Kelp, straight from the product label.

Brand Nature's Harmony
Net contents 250 Capsule(s)
Market status On market
Date entered into DSLD May 24, 2013
DSLD ID 21706
Product type Botanical With Nutrients
Supplement form Capsule
Dietary claims / uses All Other
Intended target group(s) Adult (18 - 50 Years), Gluten Free, Dairy Free
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 Norwegian Kelp by Nature's Harmony, 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)
IngredientAmount% DV
Iodine455 mcg--
Norwegian Kelp (Laminaria digitata) powder97 mg--

Other ingredients: Cellulose, Silicon Dioxide, Magnesium Stearate, Gelatin

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

Recommended Use: A source of iodine. Recommended Dose (Adults): Take 1 capsule daily with a meal.

Formulation

This product does not contain corn, dairy, eggs, gluten, soy, sulfites, or artificial colours, flavours or preservatives.

Precautions

Risk Information: Do not use if pregnant or breastfeeding.

Individuals with a thyroid condition should consult a health care practitioner before use.

KEEP OUT OF REACH OF CHILDREN.

DO NOT USE IF SEAL UNDER CAP IS BROKEN.

Storage

STORE IN A COOL, DRY PLACE.

Formula

Source of Iodine

General Statements

{Capsule} Actual Size

A Proud Canadian Company

UPC CODE TO BE: 63047 05832 8

General

400366.01-05

Seals/Symbols

SunOpta A healthy products company

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

See for yourself

Norwegian Kelp by Nature's Harmony label

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

Norwegian Kelp 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 Norwegian Kelp by Nature's Harmony

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

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

Norwegian Kelp (Laminaria digitata) powder

Interacts with
69 drugs
97 mg per serving

Laminaria is a type of brown seaweed (kelp) that is very rich in iodine and is also used in medical settings as a natural cervical dilator. Because it...

Norwegian Kelp (Laminaria digitata) powder monograph & interactions

Other (inactive) ingredients: Cellulose, Silicon Dioxide, Magnesium Stearate, Gelatin. These complete the product’s ingredient list but are not active constituents.

Interaction report

Norwegian Kelp by Nature's Harmony Drug Interactions

Want to check YOUR meds against Norwegian Kelp?

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
70Drugs
70 Moderate

Ingredients driving the most interactions

Norwegian Kelp (Laminaria digitata) powder 69

Individual Drug Interactions

The ingredients in Norwegian Kelp interact with 70 drugs. Click any drug to see the details.

1 of the 1 ingredient in Norwegian Kelp interact with drugs. Each result below shows which ingredient is responsible. Norwegian Kelp (Laminaria digitata) powder

Each ingredient & the kinds of drugs it affects

For each ingredient in Norwegian Kelp 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.

Norwegian Kelp (Laminaria digitata) powder6 drug types · 69 drugs

Ace Inhibitors (Aceis)

Theoretically, laminaria might increase the risk of hyperkalemia when taken with ACEIs.
Laminaria contains potassium.

Likelihood Possible Evidence D
Amiodarone (Cordarone)

Theoretically, combining laminaria with amiodarone might cause excessively high iodine levels.
Amiodarone contains 37.3% iodine and can increase iodine levels. Concomitant use with laminaria supplements, some of which may contain as much as 1000 mcg iodine, might increase the risk of adverse effects from iodine, including altered thyroid function.

Likelihood Possible Evidence D
Antithyroid Drugs

Due to its iodine content, laminaria might alter the effects of antithyroid drugs.
Some laminaria supplements contain up to 1000 mcg of iodine. Iodine in high doses has been reported to cause both hyperthyroidism and hypothyroidism, depending on the individual's past medical history. Taking laminaria could theoretically alter the effects of antithyroid drugs.

Likelihood Possible Evidence D
Digoxin (Lanoxin)

Theoretically, laminaria might increase the risk of hyperkalemia, which could increase the effects and adverse effects of digoxin.
Laminaria contains potassium.

Likelihood Possible Evidence D
Potassium-Sparing Diuretics

Theoretically, laminaria might increase the risk of hyperkalemia when taken with potassium-sparing diuretics.
Laminaria contains potassium.

Likelihood Possible Evidence D
Thyroid Hormone

Due to its iodine content, laminaria might alter the effects of thyroid hormone.
Some laminaria supplements contain up to 1000 mcg of iodine. Iodine in high doses has been reported to cause both hyperthyroidism and hypothyroidism, depending on the individual's past medical history. Taking laminaria could theoretically alter the effects of thyroid hormone.

Likelihood Possible Evidence D
Norwegian Kelp (Laminaria digitata) powder full monograph & interactions
The maker

Brand information

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

Nature's Harmony

See all Nature's Harmony products
Name
SunOpta Inc.
Street Address
6 Commerce Crescent
City
Acton
State
ON
ZipCode
L7J 2X3
Pharmacist Counseling Corner

Norwegian Kelp by Nature's Harmony: Common Questions

Does Norwegian Kelp by Nature's Harmony interact with any medications?
Yes. Based on its ingredients, Norwegian Kelp has a known interaction with 70 medications. Use the checker to see how it interacts with a specific drug.
How can one product interact with so many drugs?
Norwegian Kelp 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.
Does iodine actually prevent thyroid problems after radiation?
Yes — iodine is likely effective at protecting your thyroid if you're exposed to radioactive iodine. Your doctor or public health authority will tell you when and how much to take.
Can I take this if I have a shellfish allergy?
That depends on your specific allergy. True iodine hypersensitivity is rare; most 'iodine allergies' are actually reactions to shellfish proteins or other agents. Talk to your doctor or pharmacist about your allergy history before taking this.
What side effects might I notice?
Most commonly, abdominal upset, diarrhea, nausea, metallic taste, or headache. Serious allergic reactions are rare but possible. Stop and contact your doctor if you notice swelling, difficulty breathing, or widespread skin reactions.
Is it safe in pregnancy?
Adequate iodine is important in pregnancy for your baby's development, but only take the amount your doctor recommends — don't use high-dose products without medical guidance.
Can I breastfeed while taking this?
Some iodine passes into breast milk. Follow your doctor's recommendation on dosage to make sure both you and your baby get enough without getting too much.
What is Norwegian kelp, and why is it in this product?
Norwegian kelp is a seaweed (Laminaria digitata) that naturally contains iodine. It's used here as the source of iodine rather than a synthetic salt.

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.

Norwegian Kelp label
Go deeper

The Full Monographs Behind Norwegian Kelp’s Ingredients

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

Herb & supplement monograph

Laminaria

Interacts with 69 drugs

Laminaria is a type of brown seaweed (kelp) that is very rich in iodine and is also used in medical settings as a natural cervical dilator. Because its iodine content can be high and variabl...

Read the full Laminaria monograph → Herb & supplement monograph

Iodine

Interacts with 7 drugs

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...

Read the full Iodine monograph →
Sources

Sources & How We Checked

Norwegian Kelp'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 35 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.

Iodine 26 references
  1. McEvoy GK, ed. AHFS Drug Information. Bethesda, MD: American Society of Health-System Pharmacists, 1998.
  2. Goodman GA, Rall TW, Nies AS, Taylor P. The Pharmacological Basis of Therapeutics, 9th ed.
  3. Ghent WR, Eskin BA, Low DA, Hill LP. Iodine replacement in fibrocystic disease of the breast. Can J Surg 1993;36:453-60.
  4. Potassium iodide for nuclear exposure. Pharmacist's Letter/Prescriber's Letter 2001;17(12):171214.
  5. 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.
  6. Cabezas C, Bustamante B, Holgado W, Begue RE. Treatment of cutaneous sporotrichosis with one daily dose of potassium iodide. Pediatr Infect Dis J 1996;15:352-4. PubMed
  7. 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
  8. Yarrington CD, Pearce EN. Dietary iodine in pregnancy and postpartum. Clin Obstet Gynecol 2011;54:459-70. PubMed
  9. Goel, S., Mandhani, A., Srivastava, A., Kapoor, R., Gogoi, S., Kumar, A., and Bhandari, M. Is povidone iodine an alternative to silver nitrate for renal pelvic instillation sclerotherapy in chyluria? BJU.Int 2004;94(7):1082-1085. PubMed
  10. Teng, W., Shan, Z., Teng, X., Guan, H., Li, Y., Teng, D., Jin, Y., Yu, X., Fan, C., Chong, W., Yang, F., Dai, H., Yu, Y., Li, J., Chen, Y., Zhao, D., Shi, X., Hu, F., Mao, J., Gu, X., Yang, R., Tong, Y., Wang, W., Gao, T., and Li, C. Effect of iodine int
  11. Crawford, B. A., Cowell, C. T., Emder, P. J., Learoyd, D. L., Chua, E. L., Sinn, J., and Jack, M. M. Iodine toxicity from soy milk and seaweed ingestion is associated with serious thyroid dysfunction. Med J Aust. 10-4-2010;193(7):413-415. PubMed
  12. Ohkuma, M. Molluscum contagiosum treated with iodine solution and salicylic acid plaster. Int J Dermatol. 1990;29(6):443-445. PubMed
  13. Connelly KJ, Boston BA, Pearce EN, Sesser D, Snyder D, Braverman LE, Pino S, LaFranchi SH. Congenital hypothyroidism caused by excess prenatal maternal iodine ingestion. J Pediatr. 2012 Oct;161(4):760-2. PubMed
  14. Kasahara T, Narumi S, Okasora K, Takaya R, Tamai H, Hasegawa T. Delayed onset congenital hypothyroidism in a patient with DUOX2 mutations and maternal iodine excess. Am J Med Genet A. 2013 Jan;161A(1):214-7.
  15. Murcia M, Rebagliato M, Iñiguez C, Lopez-Espinosa MJ, Estarlich M, Plaza B, Barona-Vilar C, Espada M, Vioque J, Ballester F. Effect of iodine supplementation during pregnancy on infant neurodevelopment at 1 year of age. Am J Epidemiol. 2011 Apr 1;173(7):8 PubMed
  16. Sang Z, Wang PP, Yao Z, Shen J, Halfyard B, Tan L, Zhao N, Wu Y, Gao S, Tan J, Liu J, Chen Z, Zhang W. Exploration of the safe upper level of iodine intake in euthyroid Chinese adults: a randomized double-blind trial. Am J Clin Nutr. 2012 Feb;95(2):367-73 PubMed
  17. Speeckaert MM, Speeckaert R, Wierckx K, Delanghe JR, Kaufman JM. Value and pitfalls in iodine fortification and supplementation in the 21st century. Br J Nutr. 2011 Oct;106(7):964-73. PubMed
  18. Yun SE, Kang Y, Bae EJ, Hwang K, Jang HN, Cho HS, Chang SH, Park DJ. Iodine-induced thyrotoxic hypokalemic paralysis after ingestion of Salicornia herbace. Ren Fail. 2014 Apr;36(3):461-3.
  19. Iodine Hypersensitivity. Pharmacist's Letter/Prescriber's Letter 2011; 27(5):270504.
  20. Hammel JA, Selby JC. Pustular eruption in a patient with cancer treated with complementary and alternative medicine. JAMA Dermatology 2017 October; E1. doi: 10.1001/jamadermatol.2017.3749. [Epub ahead of print] PubMed
  21. Gil GS, Smith BW, Guerra JR, Williams WT. Acute Delirium in a Hypothyroid Patient Precipitated by Iodine Supplements Use. Am J Ther. 2018;25(6):e717-e718. PubMed
  22. Hamby T, Kunnel N, Dallas JS, Wilson DP. Maternal iodine excess: an uncommon cause of acquired neonatal hypothyroidism. J Pediatr Endocrinol Metab. 2018;31(9):1061-1064. PubMed
  23. Censi S, Watutantrige-Fernando S, Groccia G, et al. The Effects of Iodine Supplementation in Pregnancy on Iodine Status, Thyroglobulin Levels and Thyroid Function Parameters: Results from a Randomized Controlled Clinical Trial in a Mild-to-Moderate Iodine
  24. Rovner MS, Wolf BJ, Rubin M, et al. Instillation of 5% Povidone-Iodine Ophthalmic Drops Decreases the Respiratory Rate in Children Undergoing Strabismus Surgery: A Randomized Controlled Trial. J Pediatr Ophthalmol Strabismus. 2019;56(6):378-382. PubMed
  25. Guenezan J, Garcia M, Strasters D, et al. Povidone Iodine Mouthwash, Gargle, and Nasal Spray to Reduce Nasopharyngeal Viral Load in Patients With COVID-19: A Randomized Clinical Trial. JAMA Otolaryngol Head Neck Surg. 2021;147(4):400-401. PubMed
  26. Li F, Wan S, Zhang L, et al. A Meta-Analysis of the Effect of Iodine Excess on the Intellectual Development of Children in Areas with High Iodine Levels in their Drinking Water. Biol Trace Elem Res 2022;200(4):1580-1590. PubMed

See these in context on the Iodine monograph →

Laminaria 9 references
  1. The Review of Natural Products by Facts and Comparisons. St. Louis, MO: Wolters Kluwer Co., 1999.
  2. Brinker F. Herb Contraindications and Drug Interactions. 2nd ed. Sandy, OR: Eclectic Medical Publications, 1998.
  3. Pye KG, Kelsey SM, House IM, et al. Severe dyserythropoeisis and autoimmune thrombocytopenia associated with ingestion of kelp supplement. Lancet 1992;339:1540.
  4. Kazzi GM, Bottoms SF, Rosen MG. Efficacy and safety of Laminaria digitata for preinduction ripening of the cervix. Obstet Gynecol 1982;60:440-3..
  5. Harrell BL, Rudolph AH. Letter: Kelp diet: A cause of acneform eruption. Arch Dermatol 1976;112:560.
  6. Eliason BC. Transient hyperthyroidism in a patient taking dietary supplements containing kelp. J Am Board Fam Pract 1998;11:478-80. PubMed
  7. Norman JA, Pickford CJ, Sanders TW, Waller M. Human intake of arsenic and iodine from seaweed-based food supplements and health foods available in the UK. Food Addit Contam 1988;5:103-9.. PubMed
  8. Amster E, Tiwary A, Schenker MB. Case report: potential arsenic toxicosis secondary to herbal kelp supplement. Environ Health Perspect 2007;115:606-8. PubMed
  9. Miyai K, Tokushige T, Kondo M; Iodine Research Group. Suppression of thyroid function during ingestion of seaweed "Kombu" (Laminaria japonoca) in normal Japanese adults. Endocr J. 2008 Dec;55(6):1103-8. Epub 2008 Aug 9.

See these in context on the Laminaria 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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