Yes, it's true that cholecalciferol (vitamin D3) is used in rodenticides, but only in extremely high doses.
This form of vitamin D is actually the same one your skin naturally produces from sunlight, which is why it's considered the most effective and bioavailable for supplements.
The concern comes from what happens at toxic levels ... when rodents (or humans) are exposed to massive amounts, it can lead to calcium overload & organ damage. But the doses used in supplements are tiny and safe, carefully formulated to support healthy vitamin D levels, especially when sun exposure is low.
Vitamin D3 itself isn’t toxic ... it’s the dose that can have negative effects. But in the right amount, vitamin D3 is incredibly beneficial for bone, immunity, and hormone health.