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★☆☆Contested — the evidence disagrees with itself, or the finding carries a caution. A caution or conflict always shows one star, however strong the sources are.
No published study pairs oregano oil with blood thinners
Oregano appears on lists of herbs that may raise bleeding risk, but the review behind that names no way it could work and no study of it with blood-thinning drugs.
What the study found
The oregano and blood-thinner warning has no study of the pair
A review of herbs that may affect bleeding lists oregano on limited observations, names no way it could act, and says nothing is known about it alongside blood-thinning drugs. The common advice to avoid the pair is a precaution repeated from source to source, not a measured risk.
The caveat · Untested is not the same as safe
An untested pairing is not a safe one; a bleeding effect has not been measured either way. A US trial of how oregano changes the body's handling of a set of drugs has been recruiting since 2024 and has posted no results.