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Open WellbeingWhat the studies actually measured

Skin, hair and nails

Biotin (vitamin B7)and Nail plate thickness

Both sources here measured higher nail plate thickness.

How sure anyone can be

Very low certainty, level 1 of 4

Any estimate here is very uncertain.

The most certain of the two findings here; each record carries its own.

The numbers reported

25 percent change
% increase in nail plate thickness, before vs after biotin

One further source recorded only which way the numbers went, without a number.

None of these sources gave a likely range — the band the real answer probably sits in — so how precise these numbers are is still an open question here.

Two sources, newest first

What we read is the published abstract, not the full paper, so a blank below may still be printed in the paper itself. A fixed rule worked this out from the source’s own fields. Nobody checked this rating by hand.

  • Another kind of study, 2018

    Very low certainty, level 1 of 4

    Biotin for the treatment of nail disease: what is the evidence?

    J Dermatolog Treat. 2018;29(4):411-414. doi:10.1080/09546634.2017.1395799. PMID:29057689.

    Number reported
    Not in the abstract
    Which way it went
    Higher
    Likely range
    Not in the abstract
    Source’s own words
    not reported (direction only)
    Who was studied
    Adult with brittle nails
    Compared with
    not stated in the abstract
    Amount taken
    Not in the abstract
    For how long
    Not in the abstract
    Disagreement between studies
    Not in the abstract
    Kind of record
    Journal article
    How this rating was reachedstarts at Low, 2 steps down: risk of bias and imprecision
    1. Starts at Low
    2. Risk of bias brought it down to Very lowthe abstract reports no risk-of-bias or quality appraisal, so study limitations cannot be ruled outNot in the abstract
    3. Imprecision — already at Very low, the lowest rungthe abstract reports no confidence interval for the estimateNot in the abstract
    4. Ends at Very low2 steps down.
    Checked, nothing to step it down for
    indirectness
    Inconsistency
    No disagreement reported, and no count of studies behind it

    Imprecision stops at the first check that applies; others may apply too.

    AI-reviewed & signed — an AI agent re-read this finding against the saved source and checked that the quote, the numbers, the units and the direction match it. No person read it. The owner authorised the agent to sign the batch with the owner's key, and every build rechecks that signature against these exact bytes.

    Read the abstract on PubMed

  • Case series, 1990 · 8 participants

    Very low certainty, level 1 of 4

    Treatment of brittle fingernails and onychoschizia with biotin: scanning electron microscopy.

    J Am Acad Dermatol. 1990;23(6 Pt 1):1127-32. doi:10.1016/0190-9622(90)70345-i. PMID:2273113.

    Number reported
    25 percent change
    Which way it went
    Higher
    Likely range
    Not in the abstract
    Source’s own words
    % increase in nail plate thickness, before vs after biotin
    Who was studied
    Adult with brittle nails
    Compared with
    none (before-after within patient)
    Amount taken
    Not in the abstract
    For how long
    Not in the abstract
    Disagreement between studies
    Not in the abstract
    Kind of record
    Journal article
    How this rating was reachedstarts at Very low, 2 steps down: risk of bias and imprecision
    1. Starts at Very low
    2. Risk of bias — already at Very low, the lowest rungthe abstract reports no risk-of-bias or quality appraisal, so study limitations cannot be ruled outNot in the abstract
    3. Imprecision — already at Very low, the lowest rungthe abstract reports no confidence interval for the estimateNot in the abstract
    4. Ends at Very low2 steps down.
    Checked, nothing to step it down for
    indirectness
    Inconsistency
    One study, so there was nothing to disagree

    Imprecision stops at the first check that applies; others may apply too.

    AI-reviewed & signed — an AI agent re-read this finding against the saved source and checked that the quote, the numbers, the units and the direction match it. No person read it. The owner authorised the agent to sign the batch with the owner's key, and every build rechecks that signature against these exact bytes.

    Read the abstract on PubMed

What is still missing from these readings

  • One give no number at all, only which way it went.
  • Two give no likely range, so how precise those numbers are is unknown.
  • One do not say how many people took part.
  • Amount taken — Not in the abstract.
  • For how long — Not in the abstract.

Something nobody wrote down is never a zero and never a guess.

Still to read for Biotin (vitamin B7)

Four of the 13 things on our list for Biotin (vitamin B7) have no reading here yet:

  • Fasting insulin
  • Hair growth rate
  • Hepatic Fat Fraction
  • Vitamin B7 (Biotin)

Still to read means nobody here has got to it, not that it was tried and did nothing or that no research exists. A pairing on no list is not a gap: we never set out to read it.

Read next

This is a library, not advice. No recommendation, no dose, no diagnosis, no ranking. We never ask about your symptoms, and nothing here is tailored to you.