What does negative mean in medical terms?

Answer 1

It depends on the context.

A negative pregnancy test or negative culture means pregnancy hormone or sought-for pathogen were not found.

A negative x-ray means normal.

A pertinent negative is a "no" answer in the history that helps narrow the diagnosis. (For instance, a woman with no period for six months reports no intercourse with a man in ten years. That's a pertinent negative.)

Answer 2

It means that the person being tested has basically passed the drug test.