Radiation from unnecessary nuclear medicine test?

I received about 45 millisieverts from a nuclear medicine test that came up negative, making the radiation exposure essentially unnecessary. My question is, does that fall under the "safe" range of exposure? I was told that if I drank lots of water over 2 days the risk would be "almost zero." Also, would medical professionals be able to "get away" with lying about the type of radioactive isotope used?