Learn English: Daily Easy English Expression 0079: take it with a grain of salt
take something with a pinch/grain of salt informal to not completely believe what someone tells you, because you know that they do not always tell the truth:
Most of what he says should be taken with a pinch of salt.
to not completely believe something that you are told, because you think it is unlikely to be true:
-You have to take everything she says with a pinch of salt, because she tends to exaggerate.