Is a vendor with only in-house testing trustworthy?

In-house-only testing means the same company that makes the product also grades it. No outside party checks the identity or purity, and the entity reporting the result has a direct financial stake in it passing. That doesn't prove a vendor is dishonest, but it leaves you no way to confirm their claims. Independent labs remove that stake. Janoshik puts a unique key on each report so anyone can confirm it at verify.janoshik.com. Finnrick goes further and mostly buys samples as an anonymous customer, so the vendor can't cherry-pick a good batch. With an in-house COA alone you can't verify the named lab exists, that the batch tested matches the batch shipped, or that nothing was edited. Look for a third-party report you can check yourself. These are research-use-only materials, not approved for human consumption, and none of this is medical or dosing advice.