When you ask a medical professional a question?

When you ask a medical professional like a general doctor or specialist a question they will answer truthfully to the best of their knowledge right? I mean is it possible that they would be euphemistic and try to er up an answer to try to make you feel better. I want the truth, the straight truth of all the possibilities. Will they give it to me? No lies, no exaggerations etc. Even if it was about something in the past they are required by law to answer to the best of their knowledge right/