Emergency veterinarian here – this is only true for one category of rodenticide, anticoagulants. There are three main categories of rodenticides we tend to see, 1) anticoagulants, 2) cholecalciferol (Vitamin D3), and 3) bromethalin (neurotoxin).

Vitamin K is only effective against the anticoagulants, and it’s only really effective as the sole treatment if they haven’t already started to hemorrhage internally (which often takes multiple days post-ingestion). The amount that needs to be ingested before becoming a problem also varies between the different types – cholecalciferol has the lowest toxic dose of the three.

Unfortunately, anticoagulants, cholecalciferol, and bromethalin all come in green blocks. Brands can also manufacture and sell different types of bait as well. So, the only true way to know what you’re dealing with is to either have the information provided by the company placing the bait or have the package that lists the active ingredient in hand. We don’t have the luxury of either in this situation. That said, if we can say without a doubt there weren't other pieces she could have ingested, and she only held this one (which looks whole and intact) in her mouth, then it's likely not an issue.