Seaweed
Bladderwrack
Also known as: Fucus vesiculosus, Kelp, Rockweed, Black tang
Iodine-rich seaweed traditionally used for thyroid support, but dose is highly variable.
Last reviewed June 2026 · Evidence graded from peer-reviewed research, not editorial opinion. Educational only — not medical advice.
Daily target & upper limit
150 mcg / day · UL 1100 mcgBladderwrack has an established daily reference intake. See best forms, label synonyms, upper-limit warnings, and top-scoring supplements:
Bladderwrack dosage reference →Primary uses
- Natural iodine source
- Thyroid support (traditional)
- Metabolic support
How it works
- Natural iodine source
- Also contains fucoidan
- Traditional thyroid remedy
- Variable iodine makes dosing difficult
Dosage
- Typical range
- Varies widely - often 500-1000mg providing variable iodine
- Timing
- Morning
- With food
- Either way
- Duration
- Monitor thyroid if using long-term
- Special populations
- Those seeking natural iodine source
Forms
- Capsules
- Tincture
- Dried
Safety
Common side effects
- GI upset
- Metallic taste
- Acne
Contraindications
- Hyperthyroidism
- Hashimoto's (variable)
- Heavy metal sensitivity
Products containing Bladderwrack
Top-scoring supplements in our catalog that list Bladderwrack on the label. Each product is graded on Formulate's ingredient-level rubric — dose accuracy, form, transparency, and third-party testing.
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Evidence notes
Variable iodine content makes dosing unreliable
Grade C: Mostly observational or small trials; mechanism is plausible but unproven at scale.
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Medical disclaimer. This page is educational and does not replace advice from a qualified healthcare provider. Individual needs and risks vary — consult a professional before starting, stopping, or combining supplements, especially if you are pregnant or nursing, taking medication, or managing a health condition.