How do Janoshik and Medutest results compare on the same batch?

This is my second independent submission on material from the same supplier.

I have used one of these for a while and I am considering switching, which requires a reason.

What I care about is reproducibility, because a result I cannot repeat is not useful to me.

What does each option buy me, and what does it cost me?

Mechanically, janoshik Analytical is a testing service that reports purity, content and identity on submitted samples, and their methods and turnaround are both fast enough to be practical for this market.

Content assay uses a certified reference standard and quantifies against that standard under the same method conditions as the purity analysis.

Stated carefully, method validation documentation is available on request, which is more than most suppliers provide.

Janoshik publishes summary statistics on their website, including the number of samples tested and the range of reported values, giving you a baseline for comparison.

I would use Janoshik for the first lot from a new supplier and occasionally for spot-checking, not for every lot.

Keep Janoshik results to compare across suppliers and across time.

Start from the fact that Janoshik tests and reports content and purity from the same injection, so you get both measurements without testing twice.

Janoshik uses high-performance liquid chromatography for purity and content, with UV detection at 214 nanometres and an established method that is consistent across samples.

Concretely, the database can be searched by vendor, by compound, by date range and by result value, making it easy to benchmark a new supplier against historical data.

The limitation is that even Janoshik cannot catch every failure — they are testing a snapshot, not guaranteeing every vial.

If your result disagrees with the supplier, Janoshik's database will tell you whether you are alone or part of a pattern.

The single strongest value proposition of Janoshik is that they publish all results in a database indexed by vendor and compound, which lets you compare your result to hundreds of other users.

A submitted vial must include the lot number on the vial itself, not just on the shipping box, or Janoshik will decline the sample.

Janoshik reports include the lot number of the reference standard used, which lets you understand the traceability of the quantitation.

Worth noting that Janoshik reports are only comparable to other Janoshik reports, not to your supplier's reports or to results from other testing services.

The practical summary: submit your first lot to Janoshik and check the database for that vendor.

edited 13 Dec 2025 by tri_gly_ala — added the placebo-arm figures

Stated carefully, results from Janoshik are only comparable to other Janoshik results, not to results from any other laboratory, because the methods differ.

A result significantly outside the database range for that vendor and compound is either a real difference in quality or a different material than the database entries.

Community reviews and feedback on Janoshik are consistent across multiple forums and independent sources, suggesting the service is reliable.

One qualification: Janoshik testing is designed for supplier qualification, not for lot-by-lot production QC, so the turnaround is not suitable for every use case.

Keep Janoshik results to compare across suppliers and across time.

Specifically, if your result sits significantly below the supplier certificate, the first hypothesis should be inter-laboratory method difference, but Janoshik's database will tell you whether other users are reporting the same.

Comparison across time on the same vendor's material — three lots of vendor X spread over six months — shows whether quality is trending or stable.

The database has been publicly available for long enough that systematic biases in their reporting would be apparent and would have been flagged by users.

If your result disagrees with the supplier, Janoshik's database will tell you whether you are alone or part of a pattern.

edited 31 Aug 2025 by Dr_Wren_Halliday — removed a claim I could not source