Routine blood tests cannot definitively detect cancer, with the exception of blood cancers, according to Mayo Clinic. However, routine blood tests provide a look into what's occurring in a person's body and whether or not the organs are functioning well or affected by a possible cancer.
The complete blood count, or CBC, indicates the amounts of different types of blood cells in the body and can be used to best detect blood cancers, according to Mayo Clinic. Blood protein testing, another common blood test, can often identify certain blood proteins that are elevated when cancer is present. These tests are used as a tool to indicate overall health. A cancer diagnosis typically requires multiple types of testing.