Look along a shelf of hair supplements and you'll see biotin doses ranging from 50 micrograms to 10,000. That's a two-hundred-fold difference for the same nutrient, aimed at the same problem. Something doesn't add up.
The reference point
The Nutrient Reference Value for biotin in Great Britain is 50µg a day. That's the benchmark used on labels, and it's the figure the percentages on the back of any supplement are calculated against.
For a product to make any authorised claim about biotin at all, it has to contain at least 15% of that — 7.5µg per daily serving. That's the legal floor.
Biotin deficiency is also genuinely rare in people eating a normal mixed diet. It's found in eggs, nuts, seeds, salmon, sweet potato, and it's produced by gut bacteria too.
So why do some products contain 10,000µg?
Honestly? Because a bigger number sells better.
There's no authorised claim that scales with dose. “Biotin contributes to the maintenance of normal hair” is the claim, and it's the same claim whether a product contains 10µg or 10,000µg. A brand putting 200 times the reference intake in a capsule is not permitted to say anything more than a brand putting in a twentieth of that.
Biotin is water-soluble, so excess is largely excreted rather than stored. High doses are not generally considered harmful.
But there is one genuine, documented problem worth knowing about.
The thing high-dose biotin actually does
High-dose biotin interferes with certain blood tests. This is well documented and taken seriously by regulators and pathology labs.
Many common lab assays use a biotin-streptavidin binding step. Large amounts of circulating biotin can disrupt that chemistry and skew results — either falsely high or falsely low depending on the test design. Thyroid function tests are the most frequently affected. More seriously, troponin tests — used to diagnose heart attacks — can read falsely low, and the US FDA has issued safety communications about exactly this.
The practical advice: if you take a high-dose biotin supplement and you're having blood tests, tell whoever is taking the sample. Many labs advise pausing biotin for a period beforehand. Your GP or the lab will tell you how long.
This isn't a reason to panic, and it isn't a reason to avoid biotin. It's a reason to mention it, which almost nobody selling 10,000µg capsules does.
What we put in, and why
Cocoa Locks contains 800µg of biotin per 7g serving — 1600% of the reference intake.
That is comfortably more than you need for the claim, and comfortably less than the megadose products. We'd rather be honest about the reasoning than pretend there's science behind a bigger number:
- No authorised claim improves with a higher dose, so there's nothing to gain on that front.
- It's well clear of the 15% threshold, so the claim is properly supported rather than scraping in.
- It's a level where the blood-test interference issue is less pronounced than at 5,000–10,000µg — though you should still mention it if you're having tests.
The rest of the formula sits on the same logic: zinc 3mg (30% NRV), selenium 90µg (164%), folate 70µg (35%). All the amounts are published in full, alongside the sugar content, because you should be able to check rather than take our word for it.
Two things worth knowing about biotin claims generally
Biotin has no authorised claim for nails. This surprises people, because biotin is marketed as the nail vitamin across the entire category. It holds authorised claims for hair, skin and mucous membranes — not nails. Zinc is the nutrient with an authorised nails claim.
“Maintenance of normal hair” means what it says. It isn't a growth claim, a thickness claim or a hair-loss claim, and no biotin dose converts it into one.
The honest summary
If you're comparing hair supplements, the biotin number on the front is close to meaningless as a quality signal. What's more useful: does the brand publish every per-serving amount? Does it state claims in the authorised wording rather than inventing its own? Does it mention the blood-test issue?
Those tell you considerably more than whether a capsule contains 5,000 micrograms of something you'd struggle to be deficient in.
See every amount in Cocoa Locks · Do hair vitamins actually work?
This is general information, not medical advice. Food supplements should not be used as a substitute for a varied and balanced diet and a healthy lifestyle. If you're having blood tests, tell your doctor or nurse about any supplement you take. If you're concerned about hair loss, speak to your GP.