CleanLab-tested sea moss in the UK: what the heavy-metal reports show (2026)
- We have found only one sea moss product sold in the UK with a recent lab report we could open and read: Mighton’s Plain Sea Moss Gel (UK seller).
- Its M.
- S.
- Laboratories certificate (CR66566, 10 Aug 2026) gives lead 0.
- 07, cadmium 0.
- 72, mercury 0.
- 01 and total arsenic 5.
- 78 mg/kg for the dried sea moss, below the EU 2023/915 supplement limits for lead (3.
- 0), cadmium (1.
- 0) and mercury (0.
- 10 mg/kg).
- We label it “Partial report”, not lab verified: the certificate has no batch number, the four metal tests are marked as subcontracted outside the lab’s UKAS accreditation, and iodine was not measured.
- No sea moss gel, capsule or gummy in our directory is lab verified yet, so we do not name a “best” lab-tested sea moss for the UK.
- Kelp iodine capsules with full reports are compared on our seaweed page; the three lab-verified ones are sold by German shops.
Lab-tested kelp iodine supplements: 3 lab verified, metals and iodine dose →
Guide: iodine and heavy metals in seaweed, kelp and sea moss →
Data from published lab reports only; updated 2026-11-01. Not medical advice. Testing status can’t be bought.
Full seaweed comparison: sortable table of every product →
Lab results
| Product | Seller | Lab-test status | Pb | Cd | Hg | As | Price | Red flags |
|---|---|---|---|---|---|---|---|---|
| Mighton’s Plain Sea Moss Gel (St Lucian gold sea moss) 300 ml | Mighton’s Organic (mightons.co.uk, UK) · UK | Partial reportReport | 0.07 (well under the EU limit or below detection) | 0.72 (near the EU limit) | 0.01 (well under the EU limit or below detection) | 5.78 (no EU limit) | £9.99 / 300 ml (500 ml £14.99), plus £4.99 chilled postage (seen 26 Oct 2026). No daily serving is stated, so we can’t calculate a daily cost. UK seller; no EU seller found. | ⚠ 3 red flags
|
EU 2023/915 limits for food supplements: lead 3.0, cadmium 1.0, mercury 0.10 mg/kg. “Pass (no value)” means the certificate states compliance without a measured figure. “—” means no readable report on file.
About Seaweed
- What it is
- Brown seaweeds such as kelp (Laminaria species) and knotted wrack (Ascophyllum nodosum, often sold as “Norwegian kelp”), dried and sold in capsules mainly as a natural source of iodine; and sea moss (Irish moss or gold sea moss, red seaweeds), usually sold as a gel.
- Common forms
- Capsules of dried seaweed powder standardised to an iodine dose, or fresh sea moss gel in a refrigerated jar.
- Typical label doses
- Kelp capsules in our directory declare 100–250 µg iodine per daily capsule. The sea moss gel we list states no daily serving.
- Note
- Seaweed concentrates iodine and can take up cadmium, lead and arsenic from seawater. Iodine varies hugely between seaweeds and batches, so a measured iodine value matters as much as the metals. Germany’s BfR recommends no more than 100 µg iodine per daily dose in supplements (150 µg in pregnancy and breastfeeding). If you have a thyroid condition, are pregnant or take thyroid medicine, ask a doctor or pharmacist before taking iodine supplements.
Seaweed and sea moss have no authorised EU or GB health claims of their own. Iodine has authorised claims, but they only apply to products that provide at least 15% of the iodine reference intake per daily portion, so we don’t repeat them on these comparison pages and we make no benefit claims for sea moss.
Information only, not medical advice. Food supplements are not intended to diagnose, treat, cure or prevent any disease. Speak to a healthcare professional before use, especially if pregnant or on medication.
FAQ
Is there a lab-tested sea moss in the UK?
One product in our directory: Mighton’s Plain Sea Moss Gel, with a published M.S. Laboratories certificate (Aug 2026) that gives measured lead, cadmium, mercury and total arsenic. It is a partial report (no batch number, metals subcontracted outside the lab’s UKAS scope, no iodine), so we do not mark it lab verified. Other sea moss sellers we checked had an unnamed lab, an outdated report or no batch number, so they are not listed.
Does sea moss contain heavy metals?
Sea moss is a red seaweed, and seaweeds take up metals and arsenic from seawater, so levels depend on where and when it was harvested. The one UK sea moss report we hold measured lead 0.07, cadmium 0.72 and mercury 0.01 mg/kg, and 5.78 mg/kg total arsenic. Arsenic was not split into inorganic (more toxic) and organic forms, so the total figure alone does not show how much is the more toxic form.
How much iodine is in sea moss?
We can’t say for any product we list: the sea moss report did not measure iodine and the label gives no daily serving. Iodine varies widely between seaweeds and batches. The EU reference intake is 150 µg a day, BfR advises at most 100 µg per daily supplement dose, and the adult upper limit is 600 µg a day from all sources. If you have a thyroid condition, are pregnant or take thyroid medicine, ask a doctor or pharmacist first. Not medical advice.
What should a sea moss lab report show?
A named lab accredited to ISO/IEC 17025, with the metals inside its accredited scope; a batch number and a date within about two years; lead, cadmium, mercury and arsenic (ideally inorganic arsenic) as numbers in mg/kg; and a measured iodine value. A product page that says “lab tested” without the report itself is not enough for us to list it.
Can I get a sea moss product added?
Yes. If a brand publishes a batch report that meets these points, request it on our request-a-test page and we will check and list it, whatever the result. Listing and status can’t be bought.
Want another product tested? Request a test.