"All I want is the lab required for my colonoscopy," I said. He replied that he thought I would "want to know" what my other tests showed.

In reality, we both knew that with my good health, the chance that something would show up would be very, very unusual. Why waste the money?

Read MoreSex, lies and overspending

Unnecessary tests also increase the chance of "false positive" results, meaning something shows up that really isn't a problem. With false positive results, doctors may have to chase down why the lab result is erroneous, adding to costs and anxiety. Basically, lab tests should be used to supplement a history and physical, not replace it.

So, as an empowered patient, how can you help control laboratory costs? Have clients ask this simple question: "How will the result of this test affect my treatment?" If the doctor can't answer that question, the test is probably not needed. The answer "Just so we know" isn't good enough.

More here:

Take these key steps to control health-care costs