I know blood tests cant definitively say whether someone has cancer, but can they tell you that you dont have cancer by having a normal cell count?

Not enough: Blood test cannot either rule out or confirm cancer. Particularly the ones we get in the ED or for a healthy check up. Some tests could correlate with the presence of a cancer. They are called tumor markers. They should be checked only after the diagnosis has been established by a biopsy, then you can follow them as surrogate for response to treatment.

Not always,but it ca: Blood tests are a way of looking for early clues for a chronic illness like Cancer. Blood cancer is easily diagnosed from blood tests. But for most common cancers, we need to do a physical exam and imaging (X-ray) studies followed by a biopsy of any abnormal areas. That is how the final definite diagnosis is made. The costs can be minimsed by an experienced physician who can use his hands and comm