Depends on the isotope, of course. There are different ways it can hurt you.
If you put together a critical mass of ²³⁵U, it undergoes fission and you die in seconds without needing to ingest it.
Naturally ocurring uranium (²³³U-²³⁸U, mostly ²³⁸U) has a half-life of billions of years, so it’s very weakly radioactive. It would take a lot of it to harm you from decay radiation. Or very little if you pick a very unstable synthetic isotope outside the 233-238 range (but every element “has” such radioactive isotopes, though not in nature).
Uranium is chemically toxic, which is whal will kill you if you ingest a small amount of a common isotope.
Depends on the isotope, of course. There are different ways it can hurt you.