Kelp: how much to take
Kelp tablets are sold as a natural iodine source. Their iodine content varies enormously, so PillMath counts kelp as iodine: enter the iodine amount from the label.
Calculator Official intake Study doses Best form Safety Sources
Official daily intake
This is not an essential nutrient, so there is no official daily intake. Only study doses are shown.
Doses used in studies
These are doses tested in research, not personal advice. Some exceed the upper limit because they were short courses or given under medical care.
No study doses listed yet.
Best form and why
Practical pick
Label shows iodine (µg)
Why: Kelp iodine varies widely between products. Potassium iodide gives a precise dose; if you use kelp, pick one that states its iodine content.
Aakre I et al. 2021 · NIH Office of Dietary Supplements 2026
Food sources
Seaweeds such as kombu, wakame and nori; fish, dairy and iodised salt also give iodine.
Interactions
Too much iodine can upset thyroid function, especially with thyroid disease or thyroid medicine.
Safety
In a Norwegian study of 96 seaweed products, supplements gave 5 to 5,600 µg iodine per daily dose, and one portion of 54 products exceeded the safe limit. Choose a product that states its iodine content, or use potassium iodide instead.
Pregnant, breastfeeding, on medication, or managing a health condition? Check with a doctor or pharmacist before starting a supplement.
Sources
- Official reference EFSA (2017). Dietary Reference Values for nutrients: Summary report. EFSA Supporting Publications
- Official reference EFSA (2025). Overview on Tolerable Upper Intake Levels as derived by the SCF and the EFSA NDA Panel (version 11, August 2025). EFSA
- Official reference National Academies (NASEM) (2019). Dietary Reference Intakes: RDA, AI and UL tables (via NIH ODS Nutrient Recommendations). Food and Nutrition Board
- Study Aakre I et al. (2021). Commercially available kelp and seaweed products: valuable iodine source or risk of excess intake?. Food Nutr Res 65
- Official reference NIH Office of Dietary Supplements (2026). Iodine: fact sheet for health professionals (checked November 2026). NIH ODS
Values checked: November 12, 2026.
Fact sheets on other sites
Independent summaries to read alongside this page. PillMath is not affiliated with these sites.